Shower trap

[bsr]

Can anyone help with this shower trap? I think it's McAlpine from the late 1990s.

The trap doesn't seem to use the normal arrangement that I'm familiar with, where a rubber seal underneath is compressed by a flange on the top of the tray. There was a chromed trim ring siliconed on (now lost) and you can see the trap appears to be siliconed in and the silicone has cracked.

How would you fix this? The tray appears to be cemented to the concrete floor so is not coming up.

Thanks

 

[Madrab]

I would have expected a lock ring on top (those notches suggest there is/was one) that then screws into the base of the trap , either that or the chrome ring itself would have screwed down into the trap to pull it all together. No manufacturer would have had their trap just siliconed in.
If none of that is there any more and the bottom of the trap is all loose (pull the catch cup out and have a proper look) then replacement is the only option. That's means the tray needs to come out.