Thanks for your response-- can you be more specific as I don't have any other Mark IIIs to compare to? I assume we are talking about that big black square thingy on the left side looking at the back of the amp? To the left of the power tubes? It is nearly as tall as the tubes-- where would the 105 be printed? Would there be other numbers too? It is kind of worn at this point so I need to take a really close look.
Looking at my paperwork -- my receipt is 1/09/1985 and I took delivery in May. The amp shipped with the Mark II C Operating Manual-- it is a NO stripe, so it is highly possible that I have some left over II-C parts.