Most razors are for double edged blades. All double edge blades are interchangeable.
My understanding is that there are also single edged razors that don't work with double edged blades, but they are way less popular. /r/wicked_edge has a guide here [0] basically, buy a Vintage Gillette Super Speed Razor on ebay (or really anything you want, handles can't be that different, they're just 3 pieces of metal) and a pack of sample blades on tryablade.com
[0] https://www.reddit.com/r/wicked_edge/wiki/de_kit
https://www.reddit.com/r/wicked_edge/comments/4exeep/beginne...