[Regulator]

Does look like an older pressurant tank, being metal with the lovely aerospace weld. Most pressurant tanks now are composite overwrapped.

Another possibility is hydrazine fuel tank for ACS thrusters, used on Briz M upper stage, also Briz KM - like the one that dumped GEO-IK-2-11 into a bad orbit on 1 Feb.

In which case, not a good idea to open it. Nasty stuff...

[kitchen]

I'll pass on the warning about hydrazine.

From a couple other photos, there appears to be a pipe stub broken off, and a pipe plug opposite.

Another person reported seeing a meteor breaking up the previous night, maybe there are other parts yet to be found.