I've had 1973 and 1980 L42s through here in the past but don't have photos. The markings on the 1980 L42A1 are different and might be construed as dubious but the example you saw may have been correct. I've never seen an L42 dated 1976 or 1978. I still have one dated 1975.

I have an XL39E1 of my own that I can do photos of. Tell me exactly what you want and I'll get it done.