I have two .177 paratroopers

The two .177 paratrooper repeaters I have are slightly different?

One has no scope rail but fits the alloy frame/stock, also the repeater catch sits on on top of barrel block.

The other spare barrel & chamber does have scope rail but doesn’t fit my paratrooper stock, screw holes don’t match up & the repeater catch slots into grooves on the sides of the barrel block, rather than on top?

[https://imgur.com/gallery/DCxthTP
https://imgur.com/gallery/9DzABvk

Is it possible one has come off a wood stock version or maybe a Gamatic?