grumio
313
I think the location of 'Automatic' is OK
If I had to guess, I would say this watch is based on the cal 490 or 491.
These are the slightly uncommon sub-second variant of the much more common cal 500-505 calibres. I believe these were the first full rotor automatic calibres Omega made, and though the fashion of the time appears to have been mostly for sweep second watches, the cal 490/491 were still offered for those who wanted a sub-seconds watch.
This dial is from a watch of mine using the cal 490 which is definitely original - it has the same arrangement of the printing on the dial as yours.

I can't comment on the originality of the textured / structured finish on your dial. I have not seen one like it before, but that's not to say it is not original. Do you have any better pictures of the dial available ?
grumio
I meant..
By: mac_omega : March 6th, 2011-08:00
Hi, By "structure" I meant a kind of pattern, like silk cloth has a pattern, a structure..., like a kind of guiloche pattern, (machined) Or is the dial totally smooth - it does not look so in the picture. Do you understand what I mean? erich
More pics...
By: barrioporteno : March 7th, 2011-07:14
Thanks for all your replies. I'm still waiting for case reference number and calibre... And whether the dial is textured as it seems from the pictures... Apparently the movement should be a bumper and if so probably btw 342 to 344... Will post as soon as ...