In my experience in trying to use several of the aftermarket crowns for 6105s, both the 811x and 800x are very poor.
They have not worked out and resulted in loss of time and money. I have not done any of the work myself but in having a very tatented person on this site work on them, they did not fair well as all.
The experience i have had with them brought me too tears almost,
Time i wasted on them
$$$ wasted on them
Quality is poor
The inside dimension is short so to use it you would need to shorten the stem tube on your case for the crown to sit down on the case properly.
The slots in the side need opening up to fit on the lock pin.
The after market crowns,hands and dials for the 6105 range can be ^%£*&#% and bred a deep hatred in me of some after market parts. Note i am not saying all 6105 after market parts are *&^$$)*%^&^@ but from certain areas they are IME.
I think the answer to your last Question, has been answered Very Clearly, from all those that have had NOTHING but GRIEF,
and waisted $$$$
This is the main Reason, ORG Parts are so Coveted, and Shared sparingly.
Especially if you are wanting to Pressure test your 6105?? The 800X Crowns Much of the time, need to have the HARD 40yr old Gasket
removed and replaced. My understanding has been, The Gasket had to be Made Special, By one of the Watchmakers, that many
of us have used and trusted for longer then my few years. POINT Seiko only sold Crowns they never sold parts to rebuild the 800X crowns.
So even when finding an ORG this Crown is not so easy to Rebuild Can be done, I think the Cost was between $30 and $40.00
to Have the New gasket installed.
This was another reason Tiger Johns Find of the NOS 800X Crown was GREAT Find I also think he tried to Put New Gasket on a 6105 =8000 Crown?/
This is just another reason, things are as they are, for me it was a big help to understand why they were so difficult to come by, and even if Water /resistance is not at Issue
they are getting harder to come-by. Try to con't looking for Org Crown I trust you will be Much better off in the long Run
BTW I would be happy to Email you the Name of the Watchmaker that was offering this Service.