I’ve done a bit more digging and looking at the info I have to hand the chrome version was designated the Rd 9 mm Spotter Tracer L4 and used only in the operational weapon ( in the UK this was the Rocket 94mm LAW commonly known as LAW 80). The L3 version was brass and outdoor trainer and found in both the operational and outdoor trainer.

9mm Spotter 1.jpg 9mm Spotter Hd Stamp.jpg