Unmarked 5.45mm dummy

Can anybody provide any information about this unmarked 5.45mm dummy? It has been machined to a high standard from a non-magnetic alloy and there are patches of a dark-green stain on parts of the cartridge.
I have found a similar item pictured on municion.org - along with similar orange, red, and black cartridges - but there is no information given about any of this series.

Doesn’t anybody out there have any suggestions at all about this distinctive 5.45mm dummy?

To me it looks like a repro cartridge. Most “famous” ones were those made in the early 1980s (also aluminum) before the cartridge became available in the west.

For a real dummy the xtractor groove has the wrong shape, speaking for the fact that the cartridge was made by somebody who is not into the business.

No idea. The green staining is odd.

Where’d you get this and the x39 dummy from?

I could find out if you think it might be relevant but it isn’t my cartridge. I was sent this, and the 3 or 4 others posted at the same time, by a friend who would like them identified. I shall ask him.

Apparently this, together with the blue 7.62mm x 39mm dummy were bought from a French collector at a UK militaria show. I don’t know any more than that.