I am in France at the moment, so I have no access to my records. One problem tough: between the 40'and the 60' the year-dates stamps are very fancy. The view of the water-table was not clear enough. One thing from memory: De Jager (The Yeager) is meant to be the 'maker' of the gun instead of the customer. I will post you the names of the proofmasters and the year of manufacture soon/.
Livinus