Iron Mountain Incorporated
US ˙ NYSE ˙ US46284V1017

SecurityIRM / Iron Mountain Incorporated
InstitutionAsset Management One Co., Ltd.
Latest Disclosed Ownership547,474 shares
Latest Disclosed Value $ 55,918,994
Asset Management One Co., Ltd. reports 1.53% decrease in ownership of IRM / Iron Mountain Incorporated

On May 8, 2026 - Asset Management One Co., Ltd. filed a 13F-HR form disclosing ownership of 547,474 shares of Iron Mountain Incorporated (US:IRM) valued at $55,918,994 USD as of March 31, 2026. The entity filed a previous 13F-HR on January 27, 2026 disclosing 555,974 shares of Iron Mountain Incorporated. This represents a change in shares of -1.53% during the quarter. The current value of the position is $70,049,298 USD.

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)
2026-05-08 2026-03-31 13F IRON MTN INC DEL COM 46284V101 547,474 -8,500 -1.53 55,919 21.72 0.1649
2026-01-27 2025-12-31 13F IRON MTN INC DEL COM 46284V101 555,974 4,260 0.77 45,941 -18.32 0.1277
2025-10-22 2025-09-30 13F IRON MTN INC DEL COM 46284V101 551,714 -4,236 -0.76 56,242 -1.37 0.1630
2025-07-31 2025-06-30 13F IRON MTN INC DEL COM 46284V101 555,950 936 0.17 57,024 19.41 0.1788
2025-04-23 2025-03-31 13F IRON MTN INC DEL COM 46284V101 555,014 -7,527 -1.34 47,753 -18.94 0.1652
2025-01-30 2024-12-31 13F IRON MTN INC DEL COM 46284V101 562,541 -7,696 -1.35 58,909 -13.06 0.2024
2024-10-30 2024-09-30 13F IRON MTN INC DEL COM 46284V101 570,237 3,571 0.63 67,761 33.43 0.2411
2024-07-18 2024-06-30 13F IRON MTN INC DEL COM 46284V101 566,666 -13,536 -2.33 50,785 9.12 0.1943
2024-05-02 2024-03-31 13F IRON MTN INC DEL COM 46284V101 580,202 -9,496 -1.61 46,538 11.78 0.1794
2024-01-24 2023-12-31 13F IRON MTN INC DEL COM 46284V101 589,698 22,424 3.95 41,633 23.45 0.1676
2023-10-19 2023-09-30 13F IRON MTN INC DEL COM 46284V101 567,274 -108,110 -16.01 33,724 -12.12 0.1501
2023-07-31 2023-06-30 13F IRON MTN INC DEL COM 46284V101 675,384 4,839 0.72 38,375 8.17 0.1624
2023-04-25 2023-03-31 13F IRON MTN INC DEL COM 46284V101 670,545 -23,139 -3.34 35,479 2.03 0.1608
2023-02-06 2022-12-31 13F IRON MTN INC DEL COM 46284V101 693,684 66,419 10.59 34,773 26.08 0.1695
2022-11-04 2022-09-30 13F IRON MTN INC DEL COM 46284V101 627,265 -15,058 -2.34 27,580 -11.81 0.1403
2022-07-29 2022-06-30 13F IRON MTN INC COM 46284V101 642,323 -63,202 -8.96 31,274 -20.00 0.1469
2022-05-13 2022-03-31 13F IRON MTN INC COM 46284V101 705,525 -38,833 -5.22 39,093 -0.45 0.1526
2022-02-09 2021-12-31 13F IRON MTN INC COM 46284V101 744,358 41,969 5.98 39,270 28.68 0.1368
2021-11-02 2021-09-30 13F IRON MTN INC COM 46284V101 702,389 -75,640 -9.72 30,518 -7.31 0.1170
2021-08-03 2021-06-30 13F IRON MTN INC COM 46284V101 778,029 -29,685 -3.68 32,926 10.15 0.1225
2021-05-14 2021-03-31 13F IRON MTN INC COM 46284V101 807,714 -45,598 -5.34 29,893 19.20 0.1187
2021-02-12 2020-12-31 13F IRON MTN INC COM 46284V101 853,312 34,954 4.27 25,079 14.39 0.1033
2020-11-13 2020-09-30 13F IRON MTN INC COM 46284V101 818,358 37,352 4.78 21,924 7.57 0.1008
2020-08-14 2020-06-30 13F IRON MTN INC COM 46284V101 781,006 176,286 29.15 20,382 41.59 0.1002
2020-05-14 2020-03-31 13F IRON MTN INC COM 46284V101 604,720 -81,867 -11.92 14,395 -34.22 0.0841
2020-02-14 2019-12-31 13F IRON MTN INC COM 46284V101 686,587 -8,375 -1.21 21,882 -2.79 0.0986
2019-11-14 2019-09-30 13F IRON MTN INC COM 46284V101 694,962 -3,811 -0.55 22,509 2.91 0.1084
2019-08-14 2019-06-30 13F IRON MTN INC COM 46284V101 698,773 9,532 1.38 21,872 -10.51 0.1074
2019-05-15 2019-03-31 13F IRON MTN INC COM 46284V101 689,241 -294,591 -29.94 24,440 -23.04 0.1322
2019-02-13 2018-12-31 13F IRON MTN INC COM 46284V101 983,832 -30,570 -3.01 31,757 -8.71 0.0757
2018-11-14 2018-09-30 13F IRON MTN INC COM 46284V101 1,014,402 41,837 4.30 34,787 2.74 0.0714
2018-08-14 2018-06-30 13F IRON MTN INC COM 46284V101 972,565 -37,610 -3.72 33,859 2.00 0.0740
2018-05-14 2018-03-31 13F IRON MTN INC COM 46284V101 1,010,175 -45,454 -4.31 33,194 -16.94 0.0748
2018-02-14 2017-12-31 13F IRON MTN INC COM 46284V101 1,055,629 55,779 5.58 39,964 2.92 0.0882
2017-11-14 2017-09-30 13F IRON MTN INC COM 46284V101 999,850 77,206 8.37 38,832 22.81 0.0912
2017-08-14 2017-06-30 13F IRON MTN INC COM 46284V101 922,644 -13,706 -1.46 31,620 -4.94 0.0807
2017-05-11 2017-03-31 13F IRON MTN INC COM 46284V101 936,350 -63,999 -6.40 33,264 2.54 0.0873
2017-05-02 2016-12-31 13F/A-1 IRON MTN INC COM 46284V101 1,000,349 467,552 87.75 32,440 61.30 0.0829
2017-02-13 2016-12-31 13F IRON MTN INC COM 46284V101 1,000,349 32,440
2016-11-07 2016-09-30 13F IRON MOUNTAIN Com 46284V101 532,797 -5,011 -0.93 20,112 -5.45 0.2988
2016-08-03 2016-06-30 13F IRON MOUNTAIN Com 46284V101 537,808 82,960 18.24 21,271 39.13 0.3192
2016-05-05 2016-03-31 13F IRON MOUNTAIN Com 46284V101 454,848 -11,150 -2.39 15,289 16.19 0.2232
2016-01-28 2015-12-31 13F IRON MOUNTAIN Com 46284V101 465,998 -9,450 -1.99 13,159 -8.86 0.1964
2015-11-12 2015-09-30 13F IRON MOUNTAIN Com 46284V101 475,448 -4,072 -0.85 14,439 -3.14 0.2197
2015-08-06 2015-06-30 13F IRON MOUNTAIN Com 46284V101 479,520 -22,667 -4.51 14,907 -19.22 0.2066
2015-05-11 2015-03-31 13F IRON MOUNTAIN Com 46284V101 502,187 -11,931 -2.32 18,453 -9.92 0.2278
2015-02-09 2014-12-31 13F IRON MOUNTAIN COM 462846106 514,118 499,185 3,342.83 20,484 3,972.37 0.2658
2014-11-05 2014-09-30 13F IRON MOUNTAIN COM 462846106 14,933 -48,330 -76.40 503 -77.29 0.0069
2014-08-12 2014-06-30 13F IRON MOUNTAIN Com 462846106 63,263 18,400 41.01 2,215 82.15 0.0331
2014-05-05 2014-03-31 13F IRON MOUNTAIN COM 462846106 44,863 -2,905 -6.08 1,216 -16.66 0.0192
2014-02-05 2013-12-31 13F/A-1 IRON MOUNTAIN COM 462846106 47,768 -103 -0.22 1,459 10.11 0.0226
2014-01-29 2013-12-31 13F IRON MOUNTAIN COM 462846106 47,768 1,459
2014-02-05 2013-09-30 13F/A-1 IRON MOUNTAIN Com 462846106 47,871 1,965 4.28 1,325 7.99 0.0199
2013-11-06 2013-09-30 13F IRON MOUNTAIN Com 462846106 47,871 1,325
2014-02-12 2013-06-30 13F/A-1 IRON MOUNTAIN Com 462846106 45,906 45,906 1,227 0.0199
2013-08-05 2013-06-30 13F IRON MOUNTAIN Com 462846106 45,906 1,227
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.