I think it is highly likely that Promo's rifle has been retro fitted with a military L96 barrel? Was this your rifle Waco?
If not, then the end has been machined to accept the foresight.
---------- Post added at 12:45 PM ---------- Previous post was at 12:38 PM ----------
Gil
Early PM rifles did not have the NSN and designation on them. These preceeded the L96A1 adoption.
Once L96 production was up and running then it stands to reason that anyone wanting a PM (i.e. Police Forces) would have one made on an available receiver, which would have been an L96 designated action, because that's what they were making at the time and they are otherwise identical.
You said before that Frank's PM has the longer magazine, with plastic insert, this would date his rifle as an 85/86 PM. In fact I think I know the one he has and where it came from.
Therefore his wouldn't have the NSN on the receiver.
Promo's rifle is a 1989 PM, which post dates the L96 introduction, so his carries the NSN but the serial number shows it was not a military issue L96A1. The only difference with Promo's is that it has a military barrel, foresight and rear sight to make it look like an issued L96A1.
I suppose there may have been a transitional period when the rifles weren't marked thus, and maybe Steve Houghton's book will shed light on this.
There are different styles of markings too, some are engraved within an elongated recess, others are just engraved direct onto the receiver.
So, the answer is
Some PMs have it, others don't and it probably depends on their age.