Luc, with regards to blade type, all the post lather catcher GEM and ER razors were designed to take the same SE blade that is around today. Many of the lather catchers too.
Valet, Rolls, Wilkinson Empire are where you're going to see differences. (and razors I have no clue on )
Right, so the blade with a spine should fit most GEM and Ever Ready razors where the Feather (spineless) is more for those Valet, Rolls, etc.?