In the whole Stanley plane manufacturing history the 50's and 60's (post-war) plane models (and there-after), were never the same high quality standards as before.
For the values, it depends on a lot of things such as; untouched (not cleaned), no missing parts, the model, type and number, no breaks, and original as possible.
But you can get a good used Stanley plane as high quality as Veritas and Lie-Nielsen for a bargain.
Throw me a number and I'll send back a good guess.
mpm: just out of curiosity (and not about any in your collection) aboout how much is an average planer worth? i mean....if it was made say in the 60's, 40's?