1965 5513 servicing advice

[stewester]

Hi

I have recently purchased a 1965 5513 and I'm looking for some advice with regard to servicing, more specifically what is and isn't acceptable to replace as part of a service.

I've had an initial conversation with my usual watchmaker and he was aghast when I mentioned retaining the crown (correct twin lock) and domed acrylic crystal, as this would compromise the water resistance of the watch.

I was under the impression that switching out these parts for the most recent equivalents would be detrimental to the originality/period correctness of the watch, and would therefore be a no-no.

Should I insist on him not replacing these items, or is this not as big a deal as I think?

Any advice is most appreciated.