Hand painted Laelia
 

This photo shows a plate, which was hand painted in 1960. Painter was married to an orchid enthusiast, so it is painted from one of his plants (likely wild collected in the 1950s).

I believe that this is a Laelia anceps, but I don't know the other Mexican Laelias as well, so it just might be something different. Keep in mind that this flower is preceding line breeding.

Any guesses?

I have no idea but it is beautiful. You could always send a picture to a vendor who specializes in Laelias (Miranda Orchids?).

I'd say you right on anceps.

I agree, L. anceps. The other common Mexican Laelias, L. autumnalis and L. gouldiana, have very different petals, and I don't think that they have semi-alba forms like this either.