On my Father's apparently identical tripod the spikes are fixed; I don't recall his ever using rubber feet. Best keep off wood floors!
Yes, as I recall, my father had this tripod, as well, with rubber feet of some kind because he'd us it for a spy glass or spotting scope, sometimes on fine old hardwood floors, without difficulty but I seem to remember one very like it that did have a knurled threaded nut, about .5 inches top to bottom, with a small metal foot, sort of rectangle, that could be chosen, if the hollow leg was no damaged, by a slight dent or split from over torquing
I suppose, feet would be easy to make, using liquid (really a latex 'cream' to paint several layers yo the cleaned spike, onto an inch or so of the leg and when thick enough, each foot is placed into a short section of prepared metal pipe, like a larger round curtain rod, completely filled, sealed and secured with a holed piece of card stock, already on each leg, then turned upside down, protruding about 3/4 in. beyond the spike tips and pack filled with enough latex, to fill to the top of the tubing, and all three legs left on their head, legs straight up, for a week or two, and then given a 'finish' curing.
Years ago, inventing a safety syringe needle for medical personnel, I made some detailed models of the business end of the syringe, in latex, and used a boiling water bath to finish the curing, after the initial through and through drying.
The resulting rubber was quite durable, IMO.
Hobby shops and craft stores carry latex in about pint-sized tubs, and I have no experience in any catalyst for quick drying/setting-up, and some .5 inch acid brushes of good quality hair are needed, so look for these online or at auto shops, etc (you do no want hairs coming loose into your project) or the craft store itself.
Keep a jar of water and dish detergent or some household ammonia, to clear the brushes before they start drying up with the rubber, in fact, I believe most of these latex kits, use ammonia as the solvent for the latex.
I hope this helps whomever buys your fine little tripod/piece of history.