Help with type of framing

[eclecticcottage]

Greetings OHW!!

A friend of mine has just purchased a home built in the early 1900's (records show 1910) in northwest pa. We are tearing out the old drywall/sheetrock due to damage and to put in insulation. What we found was a particular type of construction that is true dimensional 2x4's with very wide sheathing. The studs (including load bearing)aren't sitting on a sill, rather on the subfloor which is the same wood as the wall sheathing. The studs are also turned "sideways", so the long side out vs the shorter side. The walls don't appear bowed. There's no header/Jack studs around the windows though, which we'd like to remedy (the originals were replaced with vinyl before she bought it).

Any thoughts on this framing? Is there a name for this style?

I feel like I've seen this before but can't place it.