Greetings All - I have had contact with Remington and, for what it's worth, wanted to share. A as some background, I live about 15 miles from the Big Green Huntsville facility but I learned their e-mail address for queries by perusing this site night before last. That is when I queried them. My question was that I have an R-51 stamped Charlotte, NC, do I a Gen 1 or 2, where it was made, and date of manufacture. I supplied the Serial # 00176XXR51 and got a response yesterday (pretty dadgum quick). The reply was, "Your R51 is a GEN II manufactured in 2016 at the facility in Huntsville, AL. There were no changes in the frame and those made in Charlotte were used in the Huntsville plant. Thank you for contacting Remington". So, don't know if this is helpful or makes thing clear as mud but wanted to share. Regards and out here.
That makes sense as the manufacturing/machining processes didn't change, only the people doing the work. I think I'd be more leery about the early gen 2 frames marked "Huntsville" than the "Charlotte" ones because of the learning curve with workers new to the processes.
Since Remington confirmed the serial number, you have a Gen 2. I have one with the Charlotte frame and one with the Huntsville frame. Both were bought new last year. They are the same, so no worries.