Just curious. You Old Type users do you have to use a specific (go to blade) with your OT or can you use a variety? Over the last year I've tried about six mainstream blades that I still successfully use in other razors, but to no avail with my OT's. All four of my OT's just seem to like the ole P-Lux which just gives me great consistently good comfortable shaves. Based on this morning shave I've decided that the P-Lux is now my default OT blade. I guess the answer all along was right in front of my face.
I'm still experimenting. I've worked out that I like a really sharp blade in my adjustable, and a smoother blade in my Old Type. I like a quite like SuperMax Stainless in my OT, but the best blade has been a 1960's Gillette blade. I have some 7'o clock blades to try and have been using one of the blacks in my Slim. It isn't quite right, but I think it will be great in my OT. Next week will be the test.
My old type likes Kai, GSB, and Wilkinson Sword. I haven't used it in months, my fiance took it and has had it loaded with Wilkinson blades since.
Any of your usually good blades should work well in the old. I did find with one of mine, it needed a shim under the blade. It changed the shave of that razor from moderately uncomfortable to my everyday go to bbs razor!!
I have three "Old"s, a 1906 SR, a 1919 J and a 1920s Made in Canada. They, all, give incredible shaves. I use Personnas in mine, they get along with my face. Crystals work really well for me and are my favorite; but, Reds, Lab Blues, and even the Med Prep also give great shaves.