They can't use the DGP illustration or deckplan but Mongoose can use the original ship class and designation as it is a classic Traveller ship.
CT S:9 "Variant: The Fiery class gunned escort is a variant based on the Gazelle class, the major difference being a streamlined hull."
and before that there was CT S:7
"Variants: The only major variant of the close escort is the gunned escort, a streamlined version with no other noticeable changes. This ship looks similar to the scout/courier, with only portions of the basic hull outline bulging above the plane surfaces. The gig nestles neatly beneath the ship. Finally, the L-Hyd tanks are not droppable, and the ship is restricted to ordinary performance...
Ships of the major variant type, the gunned escort, are of the Fiery class, named for energetic adjectives. Names include Fiery, Explosive, Active, and Bright."
It is also a ship that makes an appearance in T5...