In addition to the extended slide release, looks like a replacement upswept beavertail, ambi safety, and trigger too. Possibly a replacement backstrap, as it looks like it is made from stainless and is checkered, whereas the original was gray plastic and grooved. Grip screws replaced too. All of these are good modifications. And they appear to be from Wilson. The hammer is factory.
I have the same gun, but externally it is in factory condition, except I installed an arched Pachmayr backstrap and the same Wilson grip screws. Internally I installed a Wilson full length guide rod, heavy spring, and Shok-Buf to prevent frame battering. It's set up for full power loads.
Your gun was probably made in late 1991. Colt switched from a checkered front strap to a wrap around pebble finish grip in 1990. In 1992 the serial number had the suffix E added, meaning Enhanced. As far as I know, the only "enhancement" was that the grip, where it meets the trigger guard, is slightly scalloped for middle finger clearance. Big deal. Mine has the E suffix, but the rest of the serial number is only about 700 guns later. Other than the E enhancement and aftermarket parts, our guns are identical for layout and markings.
Mine is a sweet shooter. Magnum power, very accurate, and recoil and recovery are decent. In fact, it has less and softer recoil than a Glock 20, and recovers faster. What more could you ask for in a handgun? Concealed carried mine for a while, but it's a hefty chunk. Also carried it in the woods for protection. Ballistics are between a 357 and 41 Mag, so power is not an issue for Oregon.
My only regret is not also getting one of the plain 10mm models or a Double Eagle 10mm to beat the stuffing out of.
flabigpapa, that's the first blued 10mm Gold Cup I've seen. Nice.
Johnny, the current Ed Brown beavertail safeties have a "memory groove" that does not show in the photo. Further, the frame has to be radiused to install the Ed Brown safety, and this frame looks unmolested.
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B in O, the original Ed Brown grip safety did not have the memory groove, that was added later.
Look again at the picture and compare to the pics added by flabigpapa , the frame is obviously altered, not stock. I have installed three Brown grip safeties. I think the Brown safety looks better than Wilson's and the others.
My Colt 10 is E high polish SS with a bit of custom tune from factory . Had 3 boxes of ammo, corbon 135,150 and a Winchester at 1200. Loaded 4 COLT mags with a even mix of all ammo in each mag. Target 25 yds 10 2 inch circles on two targets. No failure to feed, 150 ammo aim point center of target, all near center, all 135 printed 2 inch higher, other ammo printed 1 inch lower. Can't ask for better.