It's a WA 9 used on KOMATSU ZENOAH/REDMAX chainsaws. It uses a K10-WAT or D10-WAT (if you only need diaphragms).
Here's the parts diagram. I've also attached the service manual.
So what are you trying to learn about it?
It’s a small cc Walbro carb that’s been around awhile and is usually a good performer. Looks like the WA, WT and Tillotson HU that we’re on Stihl 028’s.