Robert Chambers,
Thanks for the offer - there is no date, but given the Crown-V it's gotta be pre-1891.
For the peanut gallery's edification, the patent info on the face is:
Ernst Schlegelmilch
Patent 39832

Recoil Rob,
According to that PDF page on German proofmarks (ref. above), post-war German guns are clearly marked with 70mm.