I have, or had, a K-H steel rim with the KR code. I thought it was for a spool hub, but maybe not. Learn something new every day ?
I looked in my 58-68 KR Parts Book....
Shows a 19 " steel rim w/ part # 43010-52R for the TT models.
The 56 K model Parts Book shows a 19 " steel rim w/ part # 43010-52 for 52-55. Same part number, but no R. That would use the early type hub. For several years, the Legends book shows 19 " wheels were a factory option.
The rim as shown above with -52KR stamping is correct for the later style hub.
Indeed, there was another steel K-H 19 " rim for the SPOOL hubs. In the same 58-68 Parts Book, it has part # 43011-49R. There's a note : Replaced by # 43009-61R.
43009-61R is the 19 " ( WM-3 ) aluminum Borrani rim. I wasn't sure if it was used on both Front and Rear hubs, but it is. The distance between the rear spool hub flanges is wider than flanges on front hubs.
BTW : An original steel 19 " KHW rim from a WR is stamped 3095-3-RC. I don't have the front wheel here, but the rim is probably the same item. The WR uses steel spool hubs with similar dimensions as what came later.