Essentially, yes, but you could see both types in use until the end of the war. Early photos of Churchills usually show BTS 3 types, and the manganese type becomes more common in the later years of the war but never seem to have replaced them completely. At least some of the Kingforce tanks, the first combat use of the Mk. III (and, I think, represented by Ian’s kit’s box art), had manganese tracks in 1943, for example, but in my neck of the woods, out of six Mk. IV AVREs landed on 1 November 1944, four has BTS 3 tracks and only two had manganese ones. Which is why I will be using the BTS 3 type, because I have photos showing them on the tank I’m building a model of :smiling3:
However, if you’re looking to make a generic Churchill Mk. III, to the best of my knowledge you can just use either type. Put on whichever strikes your fancy, or that you can actually find to buy, I would say :smiling3: