If anyone has Blackhawk 357 serial number 15237 you may be interested in this 5237 for sale. I'm not even sure 15237 is a legitimate number but it should be in the Ross range of serial numbers.
https://www.gunsinternational.com/guns-for-sale-online/revolvers/ruger-revolvers-blackhawk/ruger-blackhawk-old-model-flat-top-3-screw-frame-cal-357-magnum-1956-vintage.cfm?gun_id=101199679
https://www.gunsinternational.com/guns-for-sale-online/revolvers/ruger-revolvers-blackhawk/ruger-blackhawk-old-model-flat-top-3-screw-frame-cal-357-magnum-1956-vintage.cfm?gun_id=101199679