There are no markings to indicate 22.2/25.4 mm however it is. I need to know what size quill stem to buy online. Here is a picture. It is from a tange steel Bianchi (the emerald green with gold lettering) road bike from the 80s or 90s I believe. Sakae components. Thanks much!

Whoops, to specify I am looking for the quill to threadless adapter, so I can use my other stems and bars.

If you need to find out whether it is 22.2 or 25.4, wrap a piece of string around it, and mark where the string touches itself.

Uwrap, and measure the string. A 25.4 will measure 79.75 mm. A 22.2 will measure 69.7 mm.

If you are looking for some other recommendation, hopefully someone else will chime in.