What should a newbie like me look for?

[muskrat]

Just send it (the bike) down to me and I will look into it. I promise. 
Looks great mate.
Cheers

[LJ.]

Your more likely to get info on it's date and whom sold to if you contact the BSA Owners Club as they hold the factory records.

[gocy]

hey muskrat i may send you.....a picture of me riding her :)
LJ i will contact them, thanks
Anyway, just a cross check
Engine Number GA72**
Frame Number GA711**
I believe its not a "G" but a "C" (but that is what the papers say)
Is it a A7 Swinging Arm 1954?

[Brian]

If the letter is definitely a C and not a G then it is a 1954 A7. And looking at your picture it appears to have all the correct parts. I reckon you have got yourself a good bike Gocy.

[trevinoz]

The engine number shouldn't be GA7. More likely CA7.
The frame seems to be a CA7 type.
Trev.

[gocy]

Thanks for your info.
Are there a lot of differences from the "s" model?
And how about the frame? which one is more comfortable, swinging arm or plunger?