wrote:
Have there been thin seals, rubber donuts, or gaskets that would rest
between the bearing cages and cups to reduce the amount of water that
can contaminate bottom bracket bearings?

yes, there are several pre-cartridge designs that have them.


I wondered whether in wet
climates, say England, such existed, before sealed bottom brackets
appeared.

trouble is, for those kind of bb's, the moisture usually gets into the
bearing from within, not without. i.e. down the seat tube, etc. the
best solution is to drill the bb to allow water an exit rather than keep
it in where it causes harm. many higher quality frames come with
pre-drilled bb's for exactly this purpose. particularly when used in
conjunction with marine grease, such a simple device is remarkably
effective.