Hi Brithunter,
I reckon the mark on your bolt knob is an inspection mark.

The photo is showing the mark upside down, and what appears to be an "A" at the top is really a "V" when viewed right way up. The (inspection mark) crown is visible also.

With the first version of the private view mark, the letter indicating year of proofing was stamped between the "cross" of the swords/scepters.
The letter on your bolt knob is in the wrong place for it to be the private view mark, but is in the correct spot for the inspection mark.