Help re Schneider Xenar 7 1/8" F3.5 with strange serial number

I've just bought a 'Schneider Xenar 7 1/8 inch F3.5' barrel lens and the thing I don't understand is why it has an unusual serial number. It does not have a normal numeric serial number (eg 11,000,232) but is "No SC-178". It's also only labelled "SCHNEIDER", not Jos Schneider or Schneider Kreuznach or similar. It doesn't appear to be coated (but I could be wrong), so may be pre war but appears to be in good condition (mostly anyway) and looks much more like any lens made form the 50's or so.



I don't know if it's some weird fake or just an uncommon special purpose Schneider lens, maybe from the war years. Any advice would be appreciated as I can't find any references anywhere to this type of serial number on a Schneider lens.

Some pics of the lens in question:





Engraving looks odd on the focal length:



The image below is typical of Schneider numbering even for very early lenses (this ones approx 1970-80, I haven't looked it up).

 

Thanks. I've seen that and I think it refers to much earlier versions of the lens so I think it's not actually relevant to the serial number markings on my particular lens (which I'm fairly confident dates to around the 50's, or so).

 

Thanks, but I'm fairly confident it's not an enlarging lens as Xenars where always a 'taking' lens. They where (and still are) used in a range of cameras over many decades. The pics I've posted don't properly show the scale of the lens which is actually quite large and heavy, but it's proprtions certainly make it look like any normal enlarging lens. The lens is about 3 inches across and weighs approx 550 grams.