exterior main panel

I was having a jolly time inspecting what I thought was the main panel in the basement of an older home when later I found this one 100 amp breaker panel on the outside under the bushes. This is at the service entrance. So now I have to think that is the ‘main panel’ and the one in the basement turns into a sub panel and is bonded. Im far less experienced than others but I have never found a main panel on the outside of the house, but this place is ancient…maybe they did that in ‘the old days’ Is this any kind of common, and am I right in calling this the ‘main’ and the basement panel ‘sub’
thanks for input
you guys rock!!
mike in MN

Would you have found outside is the service disconnect. You are correct that the interior panel is a sub-panel. The GEC termination and main bonding jumper should be in the service disconnect not the sub-panel.

Surprisingly, in our snow, we find exterior panels is more the norm.