On a detachable carry handle.  Left side.  Whose is it?

An early Anchor Harvey?

It looks like it might be Anchor Harvey Aluminum, the number following the A usually indicates the dye used in the forging process.  The forge mark is just that, it doesn't indicate who machined and finished it...

You might try and send an IM to ARFcom member Cdenmark, I seem to recall he used to collect carry handles, he might be able to give you more information...

I've seen at least one, and maybe more, Colt handles with that forge mark.

Since manufacturers source their raw forgings from different suppliers, it doesn't tell us who made yours, though.

What is an indicator, is the fact that the top of the sight base lines up with the top of the handle forging when the sight is bottomed out, indicating it is a milspec CH.  A commercial CH would have a sight that bottoms out lower, causing the top of the sight base to drop below the top of the forging.

Your CH is milspec, possibly (probably?) Colt.

I believe that to be an A-H, not an A-1 you're looking at. Sort of a stylized H there.
That would Anchor Harvey IIRC.