Just picked up an 800A (308). Someone had it cerakoted. Guy I got it from said 1968. Threw a Simmons scope on it that I had laying around. Looking forward to seeing how it shoots. Not real easy finding info on the 800’s.
I have an 800ASM (308 c/w Mossberg scope) and a 800CV (22-250 Varmint barrel). Both shoot great. The 800ASM doesn't get much range time. I love shooting the 800CV though. Yours looks to have the bolt handle reworked or is the upscale model. I have not seen that bolt handle on a Mossberg before. I have a limit amount of information which I couldn't find just now.
That is the "flat bolt handle". It was a more expensive option on these.
I recently inherited my uncle's 800B missing the bolt. I just won an ebay auction for one.