i'm the seller of the saddle
you said "the other saddle is nice, but not 1950s, and keyhole looks not factory done, as the earlier keyholes were. plus the later stamping. It has obviously been "hotrodded," because the back leather has been trimmed as well."
First you can ask me before, i never sold junk items or if i do i ask on auction This saddle from a lot of saddle i bougth several years at Ideale factory. of course lot of ideale saddle and beautiful protopye as 53 "loch ness" 57 "criteriumdes alpes" etc and lot of other saddle Brooks,AM etc This other saddle was stock for concurence. So you can be sure this is new and absolutly not "hotrodded". For date in this stock not any saddle up to 1960, and this brooks was with other saddle date 50's you'll be sure Ideale factory have the saddle before every people.
you can see the same on velobase