7.62 No4 Mk1 Identification

[Bindi2]

G'day

I have a Fazackerly No4 Mk1 converted to 7.62mm calibre. It does not fit any of the conversions detailed in Skennerton's Lee Enfield book.
It entered police sevice in Australia in the early 1970's and was retired in the late 1970's -early 1980's. I looks like a L39A1 with an Anshutz tunnel foresight and a Central Bisley rear peep sight. Apart from the serial Number F22197 and No4 Mk1 stamps, the only other identifying mark is (Ithink) the converting gunsmith's stamp which appears on the left hans side of the action body just below the charging bridge. The stamp is 5mm in diameter. Can anyone identify the stamp?



The stamp consists of a larger capital A with a top crossbar so it looks like a seesaw. Eitherside of the A are the leeters C (on the left) and S (on the right. All letters are upper case.
Cheers

That is the stamp used to show the rifle had passed the proof test at Lithgow. The rifle description is as for a range rifle of the day