Please help me identify this old Skimmer!

[GuilliHo]

Hi! The reason why I am trying to identify this skimmer is because currently, water is only being sucked from the skimmer. This is a very old pool and it came with the house and it has been driving me crazy since nothing I've tried has worked. I already tried a float valve but it didn't work because this skimmer doesn't have the groove for the o-ring and the float valve doesn't fit pretty well. I also tried the Hayward SP1082GV Skimmer Main Drain Valve and it doesn't fit either. Studying the skimmer closer, it seems that it has its own mechanism to do this, the skimmer has the marks for "Main Drain", "Both" or "Skim", there is also a small hole between the main drain's hole and the pump's suction hole. Also there are 2 little columns (I am sorry I don't know how to call those) that seem to be there to restrict the movement of something (maybe the basket?).
It's obvious that there is something missing here, but I just can't find anything online. I already went to leslie's pool with these pictures and showed them but they don't know anything about it.

I was hoping that maybe somebody in this forum would know about this type of skimmer and could should me what's missing.

Thank you very much for your help. I've attached some pictures and I added some notes to one of them.

[Teapot]

Can't help with the make but can explain how it works.
There is no O ring, hence no O ring groove.
The pegs are there to support the weight of a full skimmer basket, not seen in your photos, do you have one?
The writing at the bottom is for a plastic cover that can be used to obscure one or other or partially to balance the flow between two skimmers if fitted. The small hole between the two ports is for the screw that attaches it. You should be able to pick one up from a pool shop they are pretty universal. Obscuring the main drain port will give you a better surface skimming action as the dirt enters from the surface. Main drains do very little but I wouldn't completely block the main drain as bacteria could grow in the pipeline, better to have a little flow.