A byf43 "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 byf44 with transitional stamps.  The interesting thing about the two transitional guns is that they are only 29 numbers apart.  I also have a byf44 that was serial numbered before this byf43 and has E/135 for both slide waffenamts.  I additionally have a magazine that is double stamped and is the only example I have ever seen or heard of.