Hoping to get your advice on vintage crown replacement. As mentioned in this thread, I recently picked up several decagonal Constellation crowns - likely service replacements. Some seem fully intact but with likely dry gaskets and others are missing the washer/gasket. See an example below.

Are the ones missing the washer/gasket repairable?

For the fully intact ones, do your watchmakers re-use the original crowns during service? Do they replace the gasket or leave them as-is?

 

In my collection, I have a lot of watches with original crowns and they are NOT waterproof anymore
If you want them waterproofed, use the new ones, if you want them original, keep the old ones, you cannot have the cake and eat it, too.

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Are the ones missing the washer/gasket repairable? Yes.