help required to identify part design

[skinnydipper]

Hi, new to the forum after recently moving to a new house with large indoor inground concrete tiled pool.
I am trying to identify the design of the sump drain. All other fittings appear to be Certikin so most likely one of their parts but the pool was installed some 40 years ago.

I couldn't tell if the sump drain had a hydrostatic valve fitted and will want to drain down at sometime to do some surface tidying. Under the main drain lid when removed there is on the side of the sump drain the main return pipe and slightly off centre is a small vertical 'spout' which is typically where you see a hydrostatic valve. I have been down with my scuba gear and had a good look as there are two oblong bossed about 1/4 inch by 1/2 inch protruding from the top of the spout looking like something for a tool spanner to be fitted for removal. The later designs of the sump drain models appear to show just a female threaded hole at the base 1.5 inch thread for a plug or hyrostatic valve to be inserted as options. It was impossible to move or lift the top off the spot and certainly looked like no sign of movement lift for a working hydro valve is currently in place. On close inspection underwater the spout extends from the base of the sump drain with a male 'outer' 1.5 inch thread but the base does not appear to be an insert and more part of the original sump drain moulding.. So assumption was possibly an internaly threaded plug into the spout however again all looks like a complete moulding as part of the whole sump drain. Attempting to try some gentle turning to see if something would unscrew just instantly broke off one of the oblong bosses which then exposed two small holes. (possibly just part of the underneath of the moulding) I am trying to understand the old design and if it was a universal design for both options and if this is specifically designed this way to just break off to allow a hydovalve to be fitted if desired. Alternatively the spout sticking out is just a long 1.5 inch male threaded plug. I am reluctant to try to see if this comes out as I do not want to damage the main sump base even if it is just screwed into the base and typically the same as the designs still today.
My plan long term is to fit and keep a hydrovalve in place so it looks like I could fit a short length female threaded 1.5 inch pipe over the current spout thread then insert my hydrovalve into the top part of the new piece of threaded pipe. I would obviously break off the othe other oblong boss on the top of the spout and just check the holes are clear to ground otherwise just open up the top of the 'plug' to a larger hole.
Sorry for the long post but I am retired design engineer so tried to put in as much info as I can but as a pool novice I would prefer the long term comfort of an installed hydrovalve before thinking of ever draining down some of the pool. I would like to undertand more though the old design of this sump drain before I decide next steps. We do live in a low lying area but weather has been good and water table low so I do understand any risks involved.

[Teapot]

Have you tried a search using Google images, sometimes helps?

[lucyjohn987]

Do search on google