Stagi 10 button missing air button - seeking assistance

[zorkiii]

Hello, I purchased a Stagi 10 button concertina used recently and found the air button was missing. The seller came down in price for me and I am am reaching out to see if anyone has any tips on where I might obtain a replacement button, and any tips on replacing it? I'm new to the concertina world and appreciate any assistance. I have a photo below showing the missing button.

 

Also I'm not sure how to tell which model I have. I attached some photos below. Checking online it looks like it might be a C1 or a C3 but having a hard time knowing the difference. When playing on the right hand with the air button and depressing the left top most button, moving in on the bellows produces C5 and moving out produces B4. Is there a method to determining which key this is set to and which model? I appreciate any assistance and thanks.

[Don Taylor]

Have you taken the end off to see if the button is inside?

 

It looks like you would need to pull those pins out (carefully) with a pair of pliers.

 

Buttons falling off inside a Stagi can occur when the little rubber tubing spacers (that hold the button up from the action lever) perish.  If it is inside and the rubber has perished then you need to replace the spacers with some better tubing.