I have a copy of records released by W&S [Webley & Scott Archives] that says:
"26 Manufacture Books .22rf .32 .38 Revolvers (Mark III; Mark III star & Mark IV)
[Line] (9) Mark IV revolvers (1943- 1943) numbers 104600- 114699"

I am new here, so I hope I am not out of line- or completely wrong- as I am not a Webly expert. Please correct me if I am wrong.
Did you mean to type Mk VI? If so, the date should be marked on the left side, below the cylinder.

Here is a link to the W&S research request form: https://www.armsresearch.co.uk/Weble...%20Request.pdf