Provisional proof was done prior to assembling or chambering the tubes. Would not these guns with uncut chambers still be required to carry the provisional proof. I know that on some USA made guns the bbls will sometimes have Belgian Provisional Proof stamps, on others it seems the tubes were thick enough the stamp was lost in finishing. I believe that in the UK a maker importing an unfinished/unchambered gun would still have to submit it for definitive proof before he could "Legally" sell it. This of course did not apply to US makers.
