This might be a dumb question, but it’s been a very long week. so cut me some slack 
Doesn’t the size of the wiring from the service drop, or where utility connects to service wires at the drip loop, to the meter base have to be sized accordingly to the amp rating? In this case there was a 200 amp main service disconnect supplied by appropriately sized SE wire from the bottom of the meter base, however the SE wire that supplied/entered the meter base on top was undersized.
Given the form factor of the meter enclosure and the size of the SE cable in the top I would say that it’s a 100 amp service.
What’s the form factor? So the SE cable at the top and the meter enclosure would need changed to be compliant with a 200 amp service then? Is that what your saying?
From the photo it appears that the meter enclosure is of a size typically used for 100 amps. I would wonder how they even got the 200 amp conductors in the terminals.
Never question the ingenuity of “get it done”/“just do it” handy men. They have their patented secrets 