Comparable stake leader
Mark Campbell Winmill
SEC ownership of Global Self Storage, Inc.
Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001031235.
Disclosed value leader
Mark Campbell Winmill
Comparable rows
50/50
Latest evidence
12 May 2026
- Public ticker
- SELF on Nasdaq
- Parsed ownership sources
-
13D/G, 3/4/5, and 13F
Source: Parsed SEC ownership filingsUse: Compare filing families carefully
- Largest SEC-reported holder
-
Mark Campbell Winmill
Ranking: Comparable ownership first, then disclosed value
- Comparable ownership rows
-
50 of 50
Meaning: Rows with safely comparable ownership %
- Latest 13D/G holder
-
Mark Campbell Winmill
Source: Latest parsed Schedule 13D/G stake
- Latest parsed ownership date
-
12 May 2026
Freshness: Most recent filing date in this holder set
- Issuer CIK
- 0001031235
- Issuer location
- Millbrook, NY
Ownership snapshot
CIK-linked ownership evidence from parsed SEC filings.
3 signals
Issuer
Names, identifiers, and filing context for this profile.
2 identity fields
Ownership snapshot
Top shareholders of Global Self Storage, Inc. (13F + 13D/G + 3/4/5)
Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.
Comparable stake leader
Mark Campbell Winmill
Disclosed value leader
Mark Campbell Winmill
Comparable rows
50/50
Latest evidence
12 May 2026
13D/G
3/4/5
13F
Lead comparable stake: 8.4%
13D/G row: Mark Campbell Winmill
Showing 1-8 of 50 holder rows.
Quick read
Mark Campbell Winmill leads the comparable SEC ownership view at 8.4%.
50 of 50 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.
Open SEC evidence
Opens Mark Campbell Winmill's linked filing trail.
Comparable ownership
Top 5
Mark Campbell Winmill
8.4%
BARD ASSOCIATES INC
2.9%
TUXIS CORP
2.7%
WINMILL & CO. INC
1.3%
Donald Klimoski II
0.86%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-8 of 50 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| Mark Campbell Winmill |
13D/G
3/4/5
President and CEO, Director
|
8.4%
|
$4,605,994
947,735 shares
|
+$601,950 | 03 Dec 2025 |
| BARD ASSOCIATES INC |
13D/G
13F
Company
|
2.9%
|
$1,661,560
330,330 shares
|
$0 | 13 Aug 2025 |
| TUXIS CORP |
3/4/5
Other*
|
2.7%
|
$1,587,074
303,758 shares
|
— | 15 May 2025 |
| WINMILL & CO. INC |
13F
3/4/5
Company · Other*
|
1.3%
from 3/4/5
|
$2,997,015
586,500 shares
|
— | 31 Mar 2026 |
| Donald Klimoski II |
3/4/5
General Counsel
|
0.86%
|
$497,525
97,554 shares
|
+$2,252 | 24 Mar 2026 |
| Thomas OMalley |
3/4/5
Chief Financial Officer
|
0.81%
|
$467,639
91,694 shares
|
— | 24 Mar 2026 |
| Power Russell E. Burke |
3/4/5
Director
|
0.34%
|
$195,104
38,181 shares
|
+$551 | 12 May 2026 |
| Power William C. Zachary |
3/4/5
Director
|
0.16%
|
$92,491
18,100 shares
|
— | 12 May 2026 |
How to read this table
Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.
Forms 3/4/5 flow
Insider trading overview
Net insider flow leans to buying over the last 12 months. Net value: +$664,494.
Buys
$664,494
Insiders: 4
Sells
$0
Insiders: 0
Net
+$664,494
Shares: +128,409
Window
Last 12 months
4 rolling buckets
Buy value
Sell value
Shares: 128,409
Shares: 0
| Window (months) | Buy shares | Sell shares | Buy value | Sell value | Net value |
|---|---|---|---|---|---|
| 0-3 | 4,000 | 0 | $21,320 | $0 | +$21,320 |
| 3-6 | 0 | 0 | $0 | $0 | $0 |
| 6-9 | 88,753 | 0 | $453,535 | $0 | +$453,535 |
| 9-12 | 35,656 | 0 | $189,639 | $0 | +$189,639 |
Reporting owners
Insider holders from Forms 3/4/5
Showing 1-10 of 10 reporting-owner rows connected to Global Self Storage, Inc.. Open a relationship link for the CIK-to-CIK filing trail.
Rows
10
Largest Forms 3/4/5 holder
Mark Campbell Winmill
Net 12M change
+$664,494
Latest report
14 May 2026
| Name | Relationship | Holdings Value | Past Year Net Change | Change % | Valuation | Report Date |
|---|---|---|---|---|---|---|
| Mark Campbell Winmill | President and CEO, Director | $1,964,543 | +$105,303 | +5.7% | Filing P/S | 14 May 2026 |
| TUXIS CORP | Other* | $1,587,074 | Filing P/S | 15 May 2025 | ||
| WINMILL & CO. INC | Other* | $764,396 | +$556,388 | +267% | Filing P/S | 28 Nov 2025 |
| Donald Klimoski II | General Counsel | $497,525 | +$2,252 | +0.45% | Mixed | 24 Mar 2026 |
| Thomas OMalley | Chief Financial Officer | $467,639 | Mixed | 24 Mar 2026 | ||
| Power Russell E. Burke | Director | $195,104 | +$551 | +0.28% | Median | 12 May 2026 |
| Power William C. Zachary | Director | $92,491 | Median | 12 May 2026 | ||
| Russell Kamerman | Assistant General Counsel | $29,506 | Mixed | 24 Mar 2026 | ||
| Sally Coonrad Carroll | Director | $21,258 | Filing P/S | 21 May 2025 | ||
| By Power George B. Langa | Director | $16,241 | Mixed | 28 Nov 2022 |
Recent insider transactions for Global Self Storage, Inc.
Showing up to 300 recent insider transactions from the last 12 months.
| Insider | Symbol | Class | Transaction | % | SEC-reported value | SEC-reported price | Shares | Shares owned | Date | Ownership |
|---|---|---|---|---|---|---|---|---|---|---|
| Mark Campbell Winmill | SELF | Common Stock | Purchase | 1.1% | $21,320 | $5.33 | 4,000 | 368,582 | 14 May 2026 | Direct |
| Power Russell E. Burke | SELF | Common Stock | Award | 0.25% | 94 | 38,181 | 12 May 2026 | Direct | ||
| Power William C. Zachary | SELF | Common Stock | Award | 0.52% | 94 | 18,100 | 12 May 2026 | Direct | ||
| Power Russell E. Burke | SELF | Common Stock | Award | 7.75% | 2,739 | 38,087 | 31 Mar 2026 | Direct | ||
| Power William C. Zachary | SELF | Common Stock | Award | 17.9% | 2,739 | 18,006 | 31 Mar 2026 | Direct | ||
| Russell Kamerman | SELF | Common Stock | Award | 9.22% | 500 | 5,925 | 24 Mar 2026 | Direct | ||
| Donald Klimoski II | SELF | Common Stock | Award | 12.8% | 11,054 | 97,554 | 24 Mar 2026 | Direct | ||
| Thomas OMalley | SELF | Common Stock | Award | 13.7% | 11,054 | 91,694 | 24 Mar 2026 | Direct | ||
| Mark C. Winmill | SELF | Common Stock | Award | 7.47% | 25,344 | 364,582 | 24 Mar 2026 | Direct | ||
| Mark Campbell Winmill | SELF | Common Stock | Purchase | 1.31% | $22,364 | $5.08 | 4,400 | 339,238 | 05 Dec 2025 | Direct |
| Mark Campbell Winmill | SELF | Common Stock | Purchase | 1.82% | $30,849 | $5.14 | 6,000 | 334,838 | 04 Dec 2025 | Direct |
| Mark Campbell Winmill | SELF | Common Stock | Purchase | 1.86% | $30,770 | $5.13 | 6,000 | 328,838 | 03 Dec 2025 | Direct |
| Donald Klimoski II | SELF | Common Stock | Purchase | 0.52% | $2,252 | $5.05 | 446 | 86,500 | 02 Dec 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 2.12% | $15,853 | $5.18 | 3,062 | 147,641 | 01 Dec 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 2.37% | $17,229 | $5.16 | 3,342 | 144,579 | 28 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 3.57% | $25,175 | $5.17 | 4,873 | 141,237 | 26 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 3.45% | $23,567 | $5.18 | 4,547 | 136,364 | 25 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 3.18% | $20,904 | $5.14 | 4,064 | 131,817 | 24 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 5.12% | $31,673 | $5.09 | 6,226 | 127,753 | 21 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 5.08% | $29,842 | $5.08 | 5,870 | 121,527 | 20 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 5.69% | $31,970 | $5.13 | 6,226 | 115,657 | 19 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 5.41% | $28,977 | $5.16 | 5,618 | 109,431 | 18 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 6.38% | $31,906 | $5.12 | 6,226 | 103,813 | 17 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 7.77% | $35,838 | $5.09 | 7,035 | 97,587 | 14 Nov 2025 | Direct |
| Power Russell E. Burke | SELF | Common Stock | Award | 0.71% | 248 | 35,348 | 13 Nov 2025 | Direct | ||
| Power William C. Zachary | SELF | Common Stock | Award | 20.4% | 2,584 | 15,267 | 13 Nov 2025 | Direct | ||
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 7.98% | $33,645 | $5.03 | 6,694 | 90,552 | 13 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 7.78% | $30,438 | $5.03 | 6,055 | 83,858 | 12 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 2.73% | $10,283 | $4.97 | 2,069 | 77,803 | 11 Nov 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 6.45% | $25,150 | $5.48 | 4,592 | 75,734 | 29 Aug 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 11.3% | $39,093 | $5.42 | 7,209 | 71,142 | 28 Aug 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 9.37% | $29,345 | $5.36 | 5,477 | 63,933 | 27 Aug 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 15.4% | $40,973 | $5.26 | 7,788 | 58,456 | 26 Aug 2025 | Direct |
| Power Russell E. Burke | SELF | Common Stock | Purchase | 0.3% | $551 | $5.24 | 105 | 35,100 | 25 Aug 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 18.3% | $40,834 | $5.22 | 7,823 | 50,668 | 25 Aug 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 5.31% | $11,122 | $5.15 | 2,160 | 42,845 | 22 Aug 2025 | Direct |
| Winmill & Co. Inc | SELF | Common Stock | Purchase | 1.25% | $2,570 | $5.12 | 502 | 40,685 | 21 Aug 2025 | Direct |
| Power William C. Zachary | SELF | Common Stock | Award | 1.16% | 146 | 12,683 | 19 Aug 2025 | Direct | ||
| Power Russell E. Burke | SELF | Common Stock | Award | 0.42% | 146 | 34,995 | 19 Aug 2025 | Direct |
* marks a reported price that did not pass the local price check.