As an A-5 enthusiast I'll say it this way:
The gun has been on the planet for over 100 years. There are many desirable features and options - today's modern shells and some of the older guns may not mix well...
2 questions for you to answer for yourself:
What do I want to do with the gun?
- Waterfowl = steel shot issues from older guns
- deer/upland = lead shot = no problem
What do I know about years of manufacture, etc:
ShotgunWorld.com = A-5 forum - read everything by Jeff Mull - The guy is awe-inspiring great, read everything he ever posted. Once you're done we can talk (about 3 years from now...)
I have a few and love them - they aren't today's girl that can suck start a 3.5", 3" & 2.75" shell without a hiccup but the original design was pretty specific. Wood options are becoming harder to find - sadly. Plain barrel, full rib, vent rib, etc - JPN mfgr had screw chokes and so on. Waaaay too many questions at this point.
If I were to but my first A-5 it would be a Light Twelve with a MOD choke (figure out the * numbers) in a 28" barrel flavor. Watch for the split forearm and/or busted buttplate - ring position makes all the difference for recoil. If I found a Magnum in MOD I may drop the coin based on wood and blue.
I regret not buying a $150 A-5 "rescue" that needed new wood. My last rescue has good wood and blue, just a crappy wood finish - $375 out the door for a 1958 model, no collector value so I may have the choke cut for screw ins or just opened up to MOD.