The serial number is 25x,xxx.
Were the serial numbers sequential from 1 up to whatever the current serial number on the newest JA-22?
My JA-22 is about a year old and is in the 1,145,xxx range.
Maybe we can come close by doing the math? Start 1977 thru 2011 = 34 years. 1145000 / 34 = 33600 or so produced every year on average?
That would place the 25x,xxx gun at about the 7th year model - 1984 maybe????
It's not the blast that kills you, it's the tumble to the bottom of the 800 foot crater.....