Question on early upper

[Johnny Peppers]

Is this an early front sight base, and what is the difference?

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[Bingo]

Is this an early front sight base, and what is the difference?

Early ones will be cast. with a 1-14 between fron sight legs (601) VP 12 for a late 601 or early 602.
No drain hole in the front sight for starters. Forged, Front & Rear of FSB will be machined. Proof will be M VP with 12 towards end of Barrel. The one pictured is forged. Circa 1964-1966.

Check out Home Retro Black Rifle

[RCS]

I have seen the early "flat" front sight base with the UP in raised letters on a Colt SP1 in the 007xx serial number range. Barrel is stamped M with the Colt triangle under the front sight base also stamped 12 near the front on the bottom. This rifle is "new" and was purchased by a collector in KC years ago.

Could Colt have changed the front sight base during the early SP1 production?