i got a custom display back for my 105.003 and the movement wobbled a bit in the case so i found a knackered watch in my bag of bits, took a gasket out of the back which was just the right size to fit into the space where the spacer is needed and bobs your uncle, job done.
the 321 deserves to be seen, but one display back in my collection is enough for me. it is important IMO to buy the watch with original caseback and then add your own display back, keeping the original back with any other parts you have for the watch.

best
Graham
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