I've seen vintage SM300 165.024 and 166.024 with both Naiad (pressure-assisted seal) and screw-down crowns. Does anybody know what the production/evolution was for these crowns? For example, was the Naiad crown fitted 64-66, and screw down from 67 onward; or, were both produced side-by-side and available as options?

I'd appreciate any/all insight and information that anybody can provide here.

cheers,
Mark

 

I have a 165.024 from 1967 according to the extract of record and it has a non screwdown crown

 

I don't think anything was that clear cut with production dates, but am fairly certain there was quite a long overlap with both styles being fitted alongside each other.
Sorry that's not much help!