The pool store didn't know what kind of skimmer valve I need

[Colin2]

I recently replaced my waterline tile, reset the coping, replastered and put in a new main drain cover, but the one last thing I need is somekind of valve for the skimmer that the pool store couldn't identify. The pool contractor I had come out before I decided to do the work instead said it was either I think a "sundance" or "sunset" pool, which is apparently a company that built pools in the San Diego area but has been out of business for twenty years.

The opening directly underneath the skimmer basket is brass and two inches in diameter. About an inch below the opening is threads and a T-section that runs off perpindicular to the downward pipe towards the pump. The continuing pipe below appears to go straight down the side of the pool, I presume to the main drain. I'll try and attach a picture, but I am not sure if it is going to help.

Any ideas or direction is much appreciated as I am unwilling to replace the entire skimmer. Thanks.