UKKeycaps wrote: Based on the font, I can say with 95% certainty that the caps in that video are Z-Series
The font on the caps in the video is the font defined in the German standard DIN 1451:1951, which is what Siemens used for doubleshot caps until the late 1980s / early 90s. The zylindrical part of the keycaps is slightly elliptical as exactly is described in a (withdrawn) Siemens patent from 1979, whereas the Devlin ones seem to be perfectly round. The colours are the well-known shades of taupe, beige (for function keys) and green (for cursor keys) that are typical for Siemens keycaps of that era. The cap mount is RAFI-like, not Cherry MX. So it is not much likely that Devlin, this little Hampshire company, incorporated in 2011, made these keycaps for a keyboard made before 1990 by big Siemens, a trust that ran its own caps production, the original moulds of which are known to be in Berlin.
Hence, I've got a hundred percent confidence that these aren't Devlin caps.