I just ask the same question and Mossberg directed me to:
cheryl@havlinsales.com
It is as they said a Mossberg M4 with M4 scope rings. I just bought one like new for $125.00 on ebay. That is the exact price Cheryl said they were going for now days. I also have the S130 peep sights for mine, they run around $50-$65. I now need the steel front and rear sights but I am not sure which ones they are.
I could use help there also. The pictures I have seen show two different ones on a M (b).
UBU
drbr.1@comcast