Iron Mountain Incorporated
MX ˙ BMV ˙ US46284V1017
SecurityMX:IRM1 / Iron Mountain Incorporated
InstitutionWelch & Forbes Llc
Latest Disclosed Ownership652,068 shares
Latest Disclosed Value $ 66,602,179
Welch & Forbes Llc reports 0.65% decrease in ownership of IRM1 / Iron Mountain Incorporated

On May 1, 2026 - Welch & Forbes Llc filed a 13F-HR form disclosing ownership of 652,068 shares of Iron Mountain Incorporated (MX:IRM1) valued at $66,602,179 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 10, 2026 disclosing 656,364 shares of Iron Mountain Incorporated. This represents a change in shares of -0.65% during the quarter.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-01 2026-03-31 13F IRON MTN INC DEL COM 46284V101 652,068 -4,296 -0.65 66,602 22.33 0.8611
2026-02-10 2025-12-31 13F IRON MTN INC DEL COM 46284V101 656,364 -2,628 -0.40 54,445 -18.95 0.6596
2025-11-04 2025-09-30 13F IRON MTN INC DEL COM 46284V101 658,992 -9,946 -1.49 67,178 -2.09 0.8091
2025-08-05 2025-06-30 13F IRON MTN INC DEL COM 46284V101 668,938 -5,104 -0.76 68,613 18.31 0.8568
2025-05-02 2025-03-31 13F IRON MTN INC DEL COM 46284V101 674,042 -5,720 -0.84 57,995 -18.83 0.7588
2025-02-07 2024-12-31 13F IRON MTN INC DEL COM 46284V101 679,762 -7,707 -1.12 71,450 -12.54 0.9186
2024-11-04 2024-09-30 13F IRON MTN INC DEL COM 46284V101 687,469 -24,416 -3.43 81,692 23.73 1.0396
2024-08-02 2024-06-30 13F IRON MTN INC DEL COM 46284V101 711,885 -15,756 -2.17 66,027 13.13 0.8811
2024-05-03 2024-03-31 13F IRON MTN INC DEL COM 46284V101 727,641 -3,937 -0.54 58,364 14.00 0.8012
2024-02-06 2023-12-31 13F IRON MTN INC DEL COM 46284V101 731,578 -6,116 -0.83 51,196 16.74 0.7733
2023-11-03 2023-09-30 13F IRON MTN INC DEL COM 46284V101 737,694 -6,830 -0.92 43,856 3.67 0.7251
2023-07-28 2023-06-30 13F IRON MTN INC DEL COM 46284V101 744,524 -161 -0.02 42,304 7.37 0.6673
2023-04-14 2023-03-31 13F IRON MTN INC DEL COM 46284V101 744,685 -5,460 -0.73 39,401 5.37 0.6672
2023-02-02 2022-12-31 13F IRON MTN INC DEL COM 46284V101 750,145 12,087 1.64 37,395 15.23 0.6702
2022-10-31 2022-09-30 13F IRON MTN INC DEL COM 46284V101 738,058 -991 -0.13 32,453 -9.82 0.6338
2022-07-22 2022-06-30 13F IRON MTN INC COM 46284V101 739,049 -7,997 -1.07 35,985 -13.07 0.6584
2022-04-25 2022-03-31 13F IRON MTN INC COM 46284V101 747,046 27,237 3.78 41,394 9.89 0.6521
2022-01-19 2021-12-31 13F IRON MTN INC COM 46284V101 719,809 -2,517 -0.35 37,668 20.02 0.5639
2021-10-13 2021-09-30 13F IRON MTN INC COM 46284V101 722,326 2,843 0.40 31,385 3.07 0.5216
2021-07-22 2021-06-30 13F IRON MTN INC COM 46284V101 719,483 -416 -0.06 30,449 14.28 0.5145
2021-04-14 2021-03-31 13F IRON MTN INC COM 46284V101 719,899 307 0.04 26,644 25.60 0.4920
2021-01-20 2020-12-31 13F IRON MTN INC COM 46284V101 719,592 8,261 1.16 21,214 11.32 0.4150
2020-10-23 2020-09-30 13F IRON MTN INC COM 46284V101 711,331 -9,270 -1.29 19,057 1.33 0.4112
2020-07-15 2020-06-30 13F IRON MTN INC COM 46284V101 720,601 -176,282 -19.65 18,807 -11.89 0.4405
2020-04-17 2020-03-31 13F IRON MTN INC COM 46284V101 896,883 -73,582 -7.58 21,345 -30.98 0.5962
2020-01-17 2019-12-31 13F IRON MTN INC COM 46284V101 970,465 23,753 2.51 30,928 0.86 0.6881
2019-10-11 2019-09-30 13F IRON MTN INC COM 46284V101 946,712 -61 -0.01 30,664 3.48 0.7318
2019-07-12 2019-06-30 13F IRON MTN INC COM 46284V101 946,773 -32,126 -3.28 29,634 -14.63 0.7214
2019-04-29 2019-03-31 13F IRON MTN INC COM 46284V101 978,899 -3,864 -0.39 34,712 8.98 0.8708
2019-02-05 2018-12-31 13F IRON MTN INC COM 46284V101 982,763 -19,887 -1.98 31,851 -7.97 0.8979
2018-10-17 2018-09-30 13F IRON MTN INC COM 46284V101 1,002,650 -5,754 -0.57 34,611 -1.97 0.8250
2018-07-16 2018-06-30 13F IRON MTN INC COM 46284V101 1,008,404 -22,092 -2.14 35,305 4.26 0.9129
2018-04-12 2018-03-31 13F IRON MTN INC COM 46284V101 1,030,496 -9,400 -0.90 33,861 -13.70 0.8726
2018-01-26 2017-12-31 13F IRON MTN INC COM 46284V101 1,039,896 -50,236 -4.61 39,236 -7.48 1.0472
2017-11-13 2017-09-30 13F IRON MTN INC COM 46284V101 1,090,132 -12,821 -1.16 42,406 11.90 1.1162
2017-07-31 2017-06-30 13F IRON MTN INC COM 46284V101 1,102,953 -19,404 -1.73 37,898 -5.34 1.0592
2017-07-31 2017-03-31 13F/A-1 IRON MTN INC COM 46284V101 1,122,357 -40,232 -3.46 40,035 6.02 1.1459
2017-04-27 2017-03-31 13F IRON MTN INC COM 46284V101 1,122,357 40,035
2017-02-07 2016-12-31 13F IRON MTN INC COM 46284V101 1,162,589 -7,070 -0.60 37,761 -13.98 1.1300
2016-11-02 2016-09-30 13F IRON MTN INC COM 46284V101 1,169,659 -37,441 -3.10 43,898 -8.70 1.5179
2016-08-02 2016-06-30 13F IRON MTN INC COM 46284V101 1,207,100 -27,267 -2.21 48,079 14.86 1.4652
2016-05-05 2016-03-31 13F IRON MTN INC COM 46284V101 1,234,367 -41,459 -3.25 41,857 21.47 1.3035
2016-01-27 2015-12-31 13F IRON MTN INC COM 46284V101 1,275,826 5,481 0.43 34,460 -12.55 1.1057
2015-11-05 2015-09-30 13F IRON MTN INC COM 46284V101 1,270,345 -916 -0.07 39,406 -0.01 1.3154
2015-08-11 2015-06-30 13F IRON MTN INC COM 46284V101 1,271,261 -61,494 -4.61 39,409 -18.94 1.2261
2015-04-30 2015-03-31 13F IRON MTN INC COM 46284V101 1,332,755 1,332,755 48,619 1.4609
2015-01-27 2014-12-31 13F IRON MTN COM 462846106 0 -1,248,582 -100.00 0 -100.00
2014-10-27 2014-09-30 13F IRON MTN COM 462846106 1,248,582 6,750 0.54 40,766 -7.40 1.2444
2014-07-31 2014-06-30 13F IRON MTN COM 462846106 1,241,832 -24,620 -1.94 44,023 26.08 1.3895
2014-05-01 2014-03-31 13F IRON MTN COM 462846106 1,266,452 1,409 0.11 34,917 -9.06 1.1060
2014-01-17 2013-12-31 13F IRON MTN COM 462846106 1,265,043 22,280 1.79 38,394 14.34 1.2156
2013-10-31 2013-09-30 13F IRON MTN COM 462846106 1,242,763 135,237 12.21 33,580 13.94 1.1304
2013-08-08 2013-06-30 13F IRON MTN COM 462846106 1,107,526 1,107,526 29,472 1.0537
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.