They are definately split rims, no tubeless wheels back then. They appear to be the non-split lock ring style, where there are 2 flat areas on the ring itself to pry it over the wheel to disassemble. I have similar wheels on my '52 6400. Here is a pic I took while breaking one down to repair the tube. You can see the notch in the ring for the pry bar. There are 2 notchs a few inches apart. Be ready for a major wrestling match.....they don't give up easily...
Use copious amounts of soapy water to lubricate....I use a strong mix of dish soap.
