Stem fitment issue - Seamaster 2846/2848 (Cal. 501)

I received a Seamaster 2846/2848 with a broken winding stem and missing crown. I’ve been working on replacing both but have run into an issue and hope someone here might have some advice.

I sourced a correct replacement crown from a user here. The crown fits correctly onto the remnants of the original broken stem, but it doesn’t thread onto what I believed was the correct replacement stem, which I found listed for the cal. 501. The new stem appears identical to the original, but under magnification, the threads seem to have a finer pitch. Otherwise, both stems measure more similarly than my calipers are able to differentiate dimensionally.

If anyone has insight, I’d appreciate it. To my knowledge, the cal. 501 should have a 0.9 mm stem diameter. I am not sure of the thread pitch as I don't have a gauge. I was under the impression that most 0.9 mm stems would have the same thread pitch. But, clearly the replacement stem I have doesn't match, so either the stem is the same diameter but with a different thread pitch, or its a different diameter entirely and my measurement tools simply are not sufficient to detect it. I’m ultimately trying to determine the correct specifications so I can source the right stem.

I've attached a few photos, though they’re not the clearest.

Regards,

Ebay. So, not exactly the highest confidence in terms of specifics.
I had looked for this spec, but I haven't found any relevant parts which state the tap size, only movement which it's intended for, and sometimes the diameter, 0.9 mm in this case. This is, in part, what caused me to take a shot at the stem I bought. I figured if it were common to have different taps on stems for this movement, more would have the tap size listed. The stem I bought functions perfectly in the movement, it just seems to be the tap issue, and yet I've found none which mention tap 9 or 10. I am operating on the assumption what I have must be tap 10, and I must need tap 9.

https://www.watchmaterial.com/omega...-stem/?searchid=0&search_query=omega+501+stem

I would think this would work, but no tap size is mentioned here either. I was hoping not to rely on trial and error, but I may have to.

Thanks Archer. Found the part matching this number and will give it a shot.