Rare or "one-of" Long Branch Target sight for No. 4 Lee Enfield

Well this might generate some head scratching. Background: many years ago, a good buddy picked up a Long Branch #4 here at the now long gone West Toronto Gun shop. When he saw it, he knew from the lack of bayonet lugs that it was in .308 cal. The salesman knew the calibre, but not the market value, so my bud got it for cheap. It didn't have the proper magazine, but he was able to get a correct Stirling mag for it to make it a repeater. Now here's where I can only speculate. There are no military possession stamps on it anywhere. I SPECULATE that it was probably hand built from select parts for a member of the Canadian Arsenals Ltd. rifle team, or as a lunch box special for a dedicated shooter. If that isn't enough Canadian content for you, check out the pics of the sight. You'll note that it conforms to neither standard pattern micrometer sight for the No.5 or No.4 rifles. As the pics show, the sight is stamped C.A.L. 1. Now, if any of you good folks have any actual, solid, first hand knowledge as to what he's got here, I'd really love to hear from you. Any practical input as to probable value would also be appreciated, and "no", it's not for sale. Anyway, I get first dibs.
https://www.milsurps.com/images/impo...ight0042-1.jpg
https://www.milsurps.com/images/impo...sight010-1.jpg

It looks like a copy of a AJP 8/53 rear sight attachment which is actually an addition to the standard No.4 rearsight and provides windage adjustment without requiring any changes to the rifle. What makes me think that is that the elevation is raised on the standard rearsight but the eyepiece is much lower. If it's DCRA rifle then the mag was often left original to use as a loading platform as a sibngle shot rifle. Is there a 4 digit number on it anywhere 2000 or less?

Looks more like a PH4 to me. but better in that when folded down the sight rests on the frame, not the knob. It looks very well made, and numbers on the frame or ladder, which are obviously for 7.62mm, look stamped rather than engraved. Either someone was very skilled indeed with the hand stamps or there was a die made up for that; notice the slight wobbles in the "CAL1" markings for comparison. We can see the legs of the frame or ladder have been milled out at the bottom to allow greater windage adjustment. Skillful bit of work, reminiscent of the experimental adjustable backsight for No4(T)s made up at RSAF(E) during the war. Interesting that there are no 50 yard increments. What are the markings on the side of the frame, minutes of angle?