Dating of Weimar-eagle/63 stamps ?

Weimar-eagle/63 stamps were used, according to what I have read, at Oberndorf from 1936 to 1939.

Is it possible to determine more precisely the time-frame when the stamps below were used ?

Maybe earlier

Deejay

Late G date (1935) lugers have the same Weimar-eagle/63. They weren't used on early G dates so just a swag would be Aug or Sep of 1935 when they started being used at Oberndorf. This may or may not correlate with 98 production.

Thank you, zf498.
The eagle which is at the top was found on a Brazilian contract Mauser which was supposedly produced around April 1937. As this export rifle shouldn't bear any Waffenamt stamp, my concern was that its rear sight slide bar might have been replaced.