The gun was almost certainly sleeved in the UK . Many people actively involved in sleeving at that time did not bother which proof house it was sent to , later some discriminated and sent london guns to London and Birmingham guns to Birmingham . If it had been sleeved in London it would have had london proof . As Webley and Scott were the only people making tubes in any quantity and demand outstripped production and costs had risen tubes were sourced from other suppliers ,Falla {?} and Delcour from belgium Verney Carron in France although these were much lighter than a lot of users wanted and from Italy .Spanish tubes were regarded as less desirable . Holland at the time had a "down" on sleeving and engraved the joints ,also their price would have been prohibitive . Belgians as far as I know did not get into sleeving in a big way as we did in Britain ,so there would have been no point in sending it there .
As it was compulsary at the time this gun was sleeved to have barrels provisonaly proofed the acceptable Belgian marks have been left visable ,later when this requirement was abandoned the marks may have been turned to be inside the ribs or struck off if not to deep .
