Measuring for a new crown

[Bill2024]

I just wanted to check what kind of a crown I need to replace this one on an old Rotary watch. 

The existing crown is smooth and almost impossible to wind the watch with (although it has not been serviced yet). Would this have been original or could it have worn down over the years?

I’m not sure what type of a crown I need. It’s not a screw-down one but is it a dust proof one? Or some other type?

Also what would I need to measure for the replacement? I can do the winding stem thread and crown depth and diameter but not sure about the tube. 

any suggestions about what to look for and where much appreciated. Thanks, Bill

Edited February 7 by Bill2024

[AndyGSi]

Crown probably is original is just worn down.

The 3 key dimensions are Diameter, Depth & Pendent Tube size.

Here's the general area to be looking on Cousins.

https://www.cousinsuk.com/product/ss-non-swiss-big-0s

[Bill2024]

6 hours ago, AndyGSi said:

The 3 key dimensions are Diameter, Depth & Pendent Tube size

Thanks Andy - sorry for dumb question, but can I just check is the pendant tube size referred to the outer diameter of the tube on the watch case?

[RichardHarris123]

7 hours ago, Bill2024 said:

Thanks Andy - sorry for dumb question, but can I just check is the pendant tube size referred to the outer diameter of the tube on the watch case?

Yes

[Bill2024]

1 hour ago, RichardHarris123 said:

Yes

Thanks.