Check out http://www.cornellpubs.com
Abby has many reprints of Midland Catalogs for sale. I know because I sent her my originals to copy.
I'd go with the 1914 catalog. It is from Midland's peak period. I have a Midland 12 SLE that is very nice. I also have a 32" bbl 12 hammer gun that is basic/plain but still has double under lugs and cross bolt.
I have seen the lesser models with a single underbite definitely made to a lower price point.

Joe