To be honest I've never heard of or seen a prefixed rifle in the "B" in this configuration that I thought was legitimate nor have I ever seen or heard of a short run in any caliber assembled in the configuration.
Ross: First, There are some dated reports that a group of unsold #1B barreled actions went back to the factory and were then stocked and had front & rear sights installed. My recollection is that Neill Bennett of Busy Bee Guns was a principal in the process. These letter as only #1B configuration rifles, and unless the staff in Records can/will access later shipping records, that #1B is the final and only configuration status one will receive.
Second, I do know of lettered 26" S-type beavertail forearm model rifles in the prefixed SN runs that have both rings and sights, cal. 6MM, 270, and 30 06.
There needs to be more studies on these uncommon variations and further, WBR should have offered them. Splitz 8)