cyq "0" series.  There is evidence that the "0" and double "0" cyq pistols were made in a different plant than the regular cyq production.  The Germans started using another plant out of the direct path of the Russian invasion to get a little more production time.   Notice that there are no E/88 stamps on this gun.  My guess is that the secondary plant out not in a waffenamt district and, therefore, no Heer inspectors were available or they had to set up a waffenamt district quickly and didn't have time to produce a standard stamp.  They seemed to have used a "U" as the inspection stamp. This example also has an unusual "SV" stamp on the left side of the slide.  The meaning and origin of this marking is unknown.  Other "0" series guns have been observed with a similar stamp in the same location.