A byf44 "q" block with transitional waffenamts stamps.  At approximately the same time Mauser changed over from 1943 to 1944 they changed the waffenamt stamp from E/135 to E/WaA135.  So you find guns with the initial slide inspection being E/135 and the final inspection being E/WaA135.   These transitional examples are considered prized collector items.  I also have a byf43 with transitional stamps.  The interesting thing about the two transitional guns is that they are only 29 numbers apart and this gun's serial number is listed in Buxton Volume II.  I additionally have a magazine that is double stamped and is the only example I have ever seen or heard of.