Oh yeah! I’ve got a low back 4 inch stainless too …. With box and shipper. Maybe my Six Series holy grail.
Also have a low back 2.75” FIXED sight Security Six in 38 Special. Don’t know how odd it is but, I was glad to get it. Only own it because a member here was vacationing in AZ and saw it in a gun store. Thank God he’s a single action guy!
On the surface these appear as just your basic common low backs.
Each have an “S” stamped behind the serial number.
I just thought is was kinda neat having both the fixed and adjustable site Security Six’s.
A lady at Ruger told me that guns returned to them from gun writers or others who got to “sample” them were frequently stamped with the “S”. Neither of these were recorded other than “returned, checked for function, stamped “S” and sold.