Questions about antique telephones

Hello all, Thank you for reading this.

Please foegive me if this is off topic or in the wrong NG.

I am very interested in old telephones from say the early 20's to late 50's
and have come across many different varieties and I'm curious about what
makes a phone collectible.

I often see references to the F1 on a handset. Does this represent an age
period for the phone or is there more to it?

Also, I have a nice Kellogg extension wall phone (no dial) that I would like
to correctly connect to today's lines to receive calls. I have tested it out
and it rings but the volume is just a bit too loud. I'm considering adding a
cap or some resistance to the receiver but I suspect I simply have it
incorrectly wired.
It's a rather small rectangular box with a round metal housing protruding
from the center of the box which houses a relay type of ringer (no bell).
The handset hangs from a hook over the center of the box not off to the
side. I would greatly appreciate it if I could get a scan of the schematics
for a phone like this or some simple guidance on retrofitting old phones.

Thanks in advance!
Jim..

jim (AT) manicarcade (DOT) com