Posted By:
leonI agree with you....
Your question to me is like asking you about T206's 
....except T206's are much more widely collected than M101-4/5 (M101) backs and talked about more. When someone asks I am usually very willing to share the little I have observed. As usual I am opposite of most and have been watching and studying these M101 backs for about 9-10 years. My thoughts are made with all due respect to Lyman and Brett (hi Lyman and Brett), of OldCardboard.com Magazine and website. They do a fantastic job and I chat with them fairly often. My personal views are the following, without regard for the different series "-4" or "-5".
most common to least common backs...
1.blank
2.sporting news
3.famous-barr
4.standard biscuit
5.the globe
6.the tribune
7.wares
8.weil
9.herpolsheimer
10.indianapolis brewing
11.gimbels- italic print
12.burgess nash
13.block and kuhl
14.gimbels- large block print
15.green joyce
16.successful farming
17.morehouse baking
18.mall theater
19.holmes to homes
20.everybodys
21.gimbels- small block print
*22.noon-day cafeteria (only seen a xerox copy)
Since the Bucyrus Brewing Company cards have blank backs they really don't count individually on the "back meter"...My guess is that some blank backs could be one of those types..
My list is not definitive by any means.
I humbly look forward to differing opinions....
warm regards