What is the time limit for filing a delayed claim for foreign priority after patent issuance?

The time limit for filing a delayed claim for foreign priority after patent issuance is specified in 37 CFR 1.55(g). According to MPEP 216.01:

‘The time period set in 37 CFR 1.55(g) for filing a claim for priority and the certified copy required under 37 CFR 1.55(f) is the later of four months from the actual filing date of the application or sixteen months from the filing date of the prior foreign application.’

However, for patents that have already been issued, the claim must be filed within the period set forth in 37 CFR 1.55(g). This typically means that the claim should be filed as soon as possible after realizing the oversight, as any delay beyond the statutory period would require explanation and potentially affect the grant of the petition.