I came along a later but a lot of the "educational materials" overlapped the era of the 50's.
U-40 insulin was most common.
Regular, sometimes NPH, sometimes Lente (don't think they make that anymore?). Some of the treatment schemes involved only one shot a day. By the 70's the "progressive" treatment methods had two shots a day of R+N, but I don't think this was common in the 50's. No concept of adjusting doses for meals.
Drugstores ran sales where a bottle of insulin was $1. I'm sure you can find ads in the newspapers (Google newspaper search?)
Glass insulin syringes, detachable big metal needles ("Luer-Lok"?). I still have a glass syringe they gave me at diagnosis (although I never used anything but plastic at home, they trained me on glass syringes, and I'm pretty sure on diagnosis in hospital, after I got off the IV's, they were giving me insulin via glass syringes). Glass syringes and needles were sterilized by some combination of putting them in a sterilizing solution (Oh, I want to say the name of this was "Yale" but memory is poor) and boiling. Again I was taught how to do this before discharge, but never actually did any of it at home because I went straight to plastic.
Insulin doses very strictly set by Doctor's orders and not tweaked. Or at least we weren't supposed to tweak them!
No home bg testing. (I was diagnosed just a little before this became widely available.) Most patients got blood taken a few times a year when they visited the doctor's office. I'd get my blood drawn, then a few days later the office would phone my parents with advice on what to do. Very very rarely I think they would show or tell me the actual number (it wasn't until college, many years after diagnosis, that the docs regularly showed me the actual numbers coming back from lab tests. And even then I think this was breaking some official rules to show the lab test directly to a patient.)
In the 1950's I'm sure some folks were still boiling down "Bendedict's Solution" for urine testing. I was diagnosed later when urine Tes-Tape and little reagent tablets that fizz and get hot when put in urine in a test tube were available but I'm pretty sure the books when I was diagnosed, still described "Benedict's Solution".
Test books filled with urine test results. Test solution or test tablet would turn different shades of colors for different "badness" of urine sugar levels. I remember the scale going "0, 1, 2, 3, 3+" or similar. If you look at the TuDiabetes group "DIABETES PHOTO MUSEUM" I think you can see some of these. Maybe this URL will work:DIABETES PHOTO MUSEUM
Most flexible diet was "exchange diet". I think if you google for "ADA Exchange Diet" you can find an updated version of it. But if you weren't lucky enough to be on the "exchange diet" the diet was very very inflexible. The dieticians ruled on approving/constructing meal plans.
No such thing as a "CDE". There were docs and nurses who specialized in diabetic education, and you might find some books/booklets from the era (again you might find in the photo museum section.)