It is possible that both Funk & Krieghoff were both outlets for Roechling Elektro Stahl but after Heinrich Krieghoff's walkabout, for sure he was rolling his own and it may be that those that wear the encircled HK were rolled in his shop. From a cursory stance, seems many a S&k drilling wore Roechling Elektro Stahl tube steel and were worked by WK:

http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=223295&page=1

Kind Regards,

Raimey
rse