X0609 4 2026-04-22 0001951222 SEALSQ Corp LAES 0002110281 O'Hara John Charles true C/O SEALSQ CORP AVENUE LOUIS-CASAI 58 COINTRIN V8 1216 SWITZERLAND true true false false Chief Financial Officer 1 Ordinary Shares 2026-04-22 4 S 0 10000 3.0561 D 296095 D Ordinary Shares 2026-04-23 4 S 0 10000 2.88 D 286095 D Ordinary Shares 2026-04-24 4 S 0 5250 2.9065 D 280845 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on October 17, 2025. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $2.97 to $3.16, inclusive. The reporting person undertakes to provide to SEALSQ Corp, any security holder of SEALSQ Corp, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnote (2) to this Form 4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $2.7884 to $3.02, inclusive. The reporting person undertakes to provide to SEALSQ Corp, any security holder of SEALSQ Corp, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnote (3) to this Form 4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $2.8234 to $2.97, inclusive. The reporting person undertakes to provide to SEALSQ Corp, any security holder of SEALSQ Corp, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnote (4) to this Form 4. /s/ John O'Hara 2026-04-24