I had
Cartridges of the World (COTW) at hand and looked under obsolete American cartridges.
The 33 WCF shows up, but not the Marlin 33 CF, and no mention of it in the blurb on the 33 WCF.
I'd want to verify, but between Marlin and other companies at the time, one would chamber their rifles for another company's cartridge, but refuse to use the other company's name in the cartridge designation OR simply tack their name onto it. THIS is what I'd hoped to find in COTW, but it wasn't there.
It does say that 33 WCF can be formed from 45-70 brass, so IF the Marlin 33CF is the same as the Winchester 33 WCF, brass should not be an issue.
Didn't see it here either:
Vintage And Antique Guns, Ammo, Knives And Other Collectable Outdoor And Historical Items.
www.ammoandguncollector.com
Not much help, but I'd look at ll the 33 WCF information availabale and see if someone mentions that Marlin chambered rifles for it, but called it something else.