Perhaps we can get someone from RobArm to answer this question, or we can make a close assumption here on the board based on serial numbers in our membership.
I have one M96 Rifle, and my brother Andy has 3. I bought mine almost as soon as I heard about them in 1999. If you think back to when these rifles were introduced, we were in the middle of the 10-year AWB, and this rifle was probably the coolest new design to appear that still complied with the AWB before it sunset in 2004.
My M96 is serial number "HP9900130X." ("X" is a number) Two of Andy's M96's are in the late 1300 range, and another is from the late 1500 serial number range. I think the serials probably started at 1000, or 1001, but that is just an assumption.
Does anyone else have an M96 with a different serial number prefix, or do they all begin with "HP"? If you could share your serial number range here, I'd be interested in determining the total production of the rifle.