Which Model of Weihrauch is this?

I bought this used off the old yellow forum years ago and never did much with it. I got it out to shoot it and realized it has no model markings on it. 

When I bought it the seller said the stock was not original. It's a .20 cal HW break barrel but I have no idea which one. Any help would be appreciated.

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Thanks!




 
The older R1s and R9s did not have open sights-they came with blued muzzle breaks and the breech blocks were not drilled and tapped for rear sight screws. I do agree you have something unusual there. Could be it started out with a longer barrel and muzzle break and later had the barrel chopped. Maybe Mike Driskill or one of our other Weirauch authories will chime in.