Hello
from research done in the italian forum "Orolgi e passioni", that Y symbol has been used by a particular crown manufacturer in the years 1956/1957 to 1959/1960. More than this I have never heard.
Another peculiarity of the Naiad is that the very initial 2915 chronograph, 2913 and 2914 instead of the classic 6.7 mm x 3.3 Naiad, used a smaller one (6.0/6.1 x 3.0/3.1 mm) signed Naiad. This is documented in early Omega catalogues.
For NIco: funnily enough, I have a Railmaster PAF of the second run. In mine however the BACK is labelled Seamaster on the outside, and with the correct reference in the inside (135.004 - 63). The whole thing has been discussed with Mr Diethelm of Omega (still active when I purchased it) who confirmed it. I know the pic is awful but was taken in a rush
BWs
Franco
