Ilford has a long history of providing specialized materials for scientific researchers. Since Kodak has almost left that market, Ilford may be about the only big company to still do this sort of semi-custom work for the scientific community. Ilford was the first company to develop effective thick emulsions for cosmic ray and high energy physics studies, and they always made the best ones. The L4 plates seem to be pretty specialized - blue sensitive and optimized for x-ray work. They are probably also pretty expensive. The Russians were isolated from western suppliers during the cold war, and I have no doubt that they developed a very good capability for themselves. I have also read that a small Russian or east European firm still makes plates for general photographic use. Unfortunately, I don't know who. At one time, not too long ago, Ilford coated FP-4 onto plates on special order. I don't know if they still do. Kodal supplied T-Max 100 on plates until a couple of years ago.