One of the guys here has a chart that breaks out the date of manufacture by the number in the gun. The 250 does tell you exactly what year it was built. The gun you have was built by Manufrance, and proofed in-house. You won’t hurt that gun running 2 3/4” loads out to about 7000-8000 psi pressure. You will either need to buy 2 1/2” low pressure loads, or, get comfortable reloading what the gun needs. It was choked MOD/FULL when it was built.
Should make a good little bird gun.

Enjoy.

Best,
Ted