No disrespect Fuff, but these front sights are completely different than any 1911. I posted several months ago trying to find the same sight, due to the same issue. I'd purchased a really nice .32 Pocket Hammerless & the slide and it's front sight were "separated" sometime during my first trip to the range.
I was unable to find the sight & tried for a good 2-months to find a replacement. I finally wrote to Colt & they sent me (at no charge I might add) an original in-the-white 1911 (not A1) sight saying that's as close as they have available. I'm a fairly adept "tinkerer" so a friend & I decided to take a shot at making it fit.
The job took about 5-hours & looks so close to the factory sight, I still can't believe it (definitely a bit of luck on our side!). There are several differences between a 1911 front sight & these:
-The overall sight body is shorter & way more narrow
-The original site is an hourglass shape viewed from the top
-The "base" (the part that sits down in the slide "bevel") is more shallow & unique.
-The sight tenon is very small & round (vs. the rectangular 1911 tenon)
We spent most of the time taking off material & getting the right hourglass shape. The tenon took about an hour by itself; you can not believe how small that thing is (think a short section of a round paper clip & you'll have it).
Also, trying to use a 1911 staking tool to mount one of these would be like trying to park a Humvee in a one-car garage. The tool is wider than the slide opening. We (very gently & slowly) used a 3/32" punch. Remember how small the tenon is, there isn't much metal that needs to be displaced.
If Colt changed the front sights during the different revisions of these pistols, the part numbers don't reflect that. The same part is listed for the .32 & .380 for all production years.
Best of luck...Funnel