Posted By:
Tim NewcombMaybe you've seen the article on M101-5/4 that Todd Schultz and I penned in the current Old Cardboard. If not I recommend it 
As far as M101-5 rarities go, yes, Cady is an extremely difficult card in M101-5 (not in M101-4). Also Becker #12 and Wallace #186. Otherwise the rarities in the set seem to involve the back varieties.
One of the fun things about this set is the multiple ways you can collect it:
1. Obviously you can try for a complete set. As you noted, Ruth, Jackson, and Thorpe are serious roadblocks.
2. One of each M101-5 back variety. That will keep you busy for a while.
3. Collect all the M101-5 cards or poses not in M101-4. That is a fun little subset, which includes Thorpe as well as Armando Marsans, Frank Chance, Becker and Wallace. But it's something to aspire to--
4. Hall of Fame set (which doesn't include Thorpe or Jackson!), or a Black Sox set.
Concerning display options: I was quite frustrated that none of the American page manufacturers made anything appropriately sized for M101-4/5. Finally when I was in London a few years ago I went to a Saturday morning swap meet in a parking garage under the Charing Cross Road tube station, and bought an album and some pages designed for British cigarette cards. They fit M101-5/4 perfectly, ten cards to a page!
You can probably find this size of album and pages on ebay from a British tobacco card seller. Even if they don't advertise albums, if you wrote and asked about them I bet one would be able to supply an appropriate album.
Feel free to email with any other questions. Best of luck--
Tim