Quick question about wear on ref. and case numbers between the lugs

[WatchFanZac]

Hello all,

I am noticing as I do research that many vintage examples I see for sale have considerable wear between the lugs partially obscuring the case and/or reference numbers.

Do members here have a theory on how the wear occurs? Does it result particularly from use with leather straps as opposed to OEM bracelets? Is it a result of sweat, sea water or other corosive? Some examples I see have pronounced wear and others have next to none. Is there an explanation for this (other than varying levels of use by their owners)?

An 16750 (c.1986) I am interested in has pristine markings between the lugs beautifully preserved. Will wearing the watch on a NATO strap cause more wear on the area than wearing it on the jubilee bracelet? I'm a fan of leather NATOs do you think it is going to speed up the wear if I put it on one?

Regards,

Zac