Magazine extension disassembly question

[iWander]

I picked up these used mags with an M&P recently and I'm not sure how to get the extensions off so I can clean them. They're filthy inside and one of the followers is sticking. Can anyone identify the brand based on the logo and how to take it apart? It looks like you push on the pin on the back and pull down but nothing's budging.
Thanks

[CWM11B]

Dont know the brand. Does that dimple contain a locking tab? From the picture, it appears to. See if you can depress it with a punch and slide that back panel up or down.

[iWander]

Thanks. Found it. They're from Falkor with a VERY tight fit.