A couple questions from Ohio

[carwashchris]

I'm confused in identifying some 1500 model's . I see quite a few 1505's that are stainless , shouldn't these be gold shell ? Also is it common for the ref # on the outside not match the inside ? Example { 1505 out 1500 in }

At about what serial # did the 1600's go from 14k to 18k as well as the 1803's

Thanks Chris