Very good question. I would have to assume that either CCSB got them or they are lost. Note that after about 1937, HMCo subbed out much (if not most or all) of their hardware. I did some research at Hart with the casting pattern cards, but that was awhile ago and I didn't spend enough time or attention to answer all the questions I have now. I think I'll need another field trip one of these days.
If you are interested in authentic hardware for your 12, I'm sure you know that Jim Reineck is the prevailing source. He does great work.