Limited license working as AB?

Can any deck rating be substituted for A/B such as 100-ton or
otherwise? (We sometimes do this on the ship I work on now, but not
sure if the Coast Guard would like that?)


No. One is a license, the other is a rating. Even an AB-OSV/special can’t run as AB on a container ship with a 1,600ton master license. Only the AB-UL will cover the position. License doesn’t matter.