I can see which posts on the lower right are for the output speakers, and the small connector labeled 'L' & 'R', but what voltage is the VCC? I'm thinking it might be 12vdc.
* Is it labelled for 8 ohm speakers? Anyway start testing with 8 since 4 ohm can draw extreme power.
* Isn't a volt rating marked on those electrolytic caps? A reasonable supply voltage is 1/2 of that volt rating.
* Touch a finger to the heatsink as you increase the volume gradually over a few minutes. Consider you're at maximum watts when it's too hot to keep your finger on.
This is definitely a class-D high power audio amp. Visually similar is this one. Based on TPA3116 chip. Definitive answer if you remove the heatsink and see what written on the IC.
* Is it labelled for 8 ohm speakers? Anyway start testing with 8 since 4 ohm can draw extreme power.
* Isn't a volt rating marked on those electrolytic caps? A reasonable supply voltage is 1/2 of that volt rating.
* Touch a finger to the heatsink as you increase the volume gradually over a few minutes. Consider you're at maximum watts when it's too hot to keep your finger on.
This is definitely a class-D high power audio amp. Visually similar is this one. Based on TPA3116 chip. Definitive answer if you remove the heatsink and see what written on the IC.
For me it gives a lot of pictures from selling sites. And on these sites you find the specifications.
Also on one of your pictures you clearly can see the part number "SKU 7944". A search on this gives hits with even more informations.
After you know it uses the TPA3116 chip --> you may do a search for the IC datasheet. As long as they designed the PCB correctly and dimensionated the parts correctly you should rely on the datasheet specifications.
But mind: When the datasheet says 30V absolute maximum, then they mean this seriously. Any voltage above this limit may immediately (within illiseconds) kill the chip. (The manufacturer may add some headroom, but I strongly recommend not to rely on this)