Ask him what the serial number prefix is, CAC = SB1, if it has the new style checkered syn stock and is NIB, it's an SB1 frame, the 357 and 44 mags have all come on SB1 frames since 2008, barrels are marked SB2 which is very misleading.
H&R won't fit high pressure barrels to any frames made prior to 2000 which is when Marlin bought H&R/NEF.
Tim