Gas Tank.....original Or Reproduction?

['72TR6RV]

Hey folks. Wondering if anyone would know how to tell the difference between a original gas tank and a reproduction tank for a 76 T140.
My 72 TR6RV tank has a welded rib from front to back on the top side. I'm confident that it has the original tank. On the T140, the tank that I got with the machine had no rib, smooth top minus the center mounting plug. I can see the thread inserts for the badges through the filler neck but not so sure about the originality of the tank. Is there any signs to look for?
Thanks for any feedback and input.

 

[Rudie]

72 TR6RV tank has a welded rib from front to back on the top side.
T140, the tank that I got with the machine had no rib, smooth top

The two tanks are basically correct, Meriden changed the press tools around late 1972-early 1973, no original '73-on tanks have seams on top.

There are underside differences between original and replica tanks, but I will need to look them up.

Ahead of a "My '7x has a tank with a centre rib" post, a centre rib, or lack of, does not affect the fitting of a tank to a frame.