It is in the smaller scale, whatever that was exactly. Some units in the smaller scale were close to the correct scale while others were way off on the smaller size. The M18 was one that comes to mind right off. I have it & the Hellcat & they are very close in actual size while Shermans & Pnzr IV G are much smaller & it is obvious with these units. If I recall correctly, 39-45 was the set when WotC got the scale right.
It was from the first sets often refereed to as V1. They ranged in scale but were somewhat consistent with 12mm. I suspect that the Archer is approx. 12mm