No such thing. Colt did make some AR15's in electroless nickel.
Is it possible you mean an AR 15 made with an elcectroless nickel finish?
100-1500 USD or so
You will have to call COLT
$1384.99
The Colt AR-15 rifle with Serial Number 100677 was manufactured in 1962. Colt's production of the AR-15 began in the early 1960s, and serial numbers from that period can be referenced to determine their manufacturing dates. For precise information, it’s best to consult Colt's official records or a reliable Colt AR-15 serial number database.
AR-15 is a trademark owned by Colt - thus, no other manufacturer may market their rifles as AR-15 unless they are specifically licenced from Colt to do such. LAR-15 is simply Rock River's alternative name to "AR-15" in order to avoid infringing on Colt's trademark.
You will have to call Colt to find out.
Colt data at Proofhouse.com
You will have to call Colt with the sn to find out.
No such sn in the AR-15 series
it was modified................
On the receiver