You're quite welcome.
That's a large part of what makes these forums so valuable.

Kuduae may / may not know if there was a particular time frame for 'C6'7' marked M1903s and / or if the 'FOREIGN MAKE' stamp is common. I have seen several images of MS with 'NOT ENGLISH MAKE' in the same zigzag boundary from about the same time period. My M1910 Take Down Model bears Austrian proofs dated 1922, also period Brit proofs, does not have the 'Not English Make' stamp.

From a thread on 'Rimfire Central':

The 'Not English Make' marking was part of the British Proof marking system during the period 1925 to 1954.
It was required on firearms obviously 'Not of English Manufacture" but also not showing any proof markings from it's country of origin that the Brits recognized as compatible with the British Proof Standards of the period.