I looked at the receivers I have. Several have either no s/n or no acceptance dates on the stamp, however I have an R-24 (.52 - 1.5) accepted 2/43, sn/ 2287 made on contract # NOs74912 and an R-25 (1.5-3) on the same contract with s/n 3105, stamped 9/43. I have an R-148 (.19-.55) stamped 9/45 (no s/n) - if this helps. - Gordon White and Dave: thanks for the card