Hi dmoze1......welcome to TFF.
Well, first off, DON'T SHOOT IT
! If you paid $650 for a New-In-Box Mk.IV Series 70 Government Model, you sure didn't hurt yourself!
Can't really tell from your photo if it's Blue or Nickel Plated, but the Blue Book value is:
Blue Finish in 100% condition - $1018
Nickel Finish in 100% condition - $1,100
My serialization list only goes up to 1978, but serial #s with a B70 suffex were made between 1979 and 1981.
Series 70s in high condition are among the most desireable of the modern Colt 1911s, and their value seems to be climbing at a faster rate than most other non-military 1911s. I'd advise you to keep it in the condition it's in and hang on to it. It can only go up in value.
Now, what's it worth?..........Hard to say. The values above are for "Plain Jane" Model 70's. Yours is obviously a "presentation piece". That can
make it more valuable, but at the same time, a bit more difficult to sell. Engraved and personalized presentation pistols are pretty much a niche market......so I really can't give you a value beyond the Blue Book value above.
History? Your guess is as good as mine. I suspect it was presented to a Customs Agent at retirement time.....but who knows? You could get a Colt Historical Letter to find out how it left the factory ( http://www.coltsmfg.com/cmci/historical.asp
) but they're quite pricey, and I doubt if the gold plating and engraving was a "factory job".
In any case, you got a helluva bargain.....keep it and enjoy it!