Thanks. It's a strange one then as it doesn't look like a repro scope that's been "modified".
From my research on here the markings seem to be in the style of the later Mk3 scopes, the "A" doesn't look like it has been added later (implying that it was made from new as a MkIA rather than an upgraded MkI?) and it has what looks like the correct part number. It also looks like it's missing it's anti-rotation peg. I've attached the vendors pictures below for info.
Attachment 108426Attachment 108427Attachment 108428Attachment 108429Attachment 108430