Elgin Grade 336

Here's an Elgin grade 336 with a photo showing the swing-out, or tip-out as they are sometimes called, case .

This case style has the advantage of have a stronger back and one less joint for moisture and dirt to get inside.  Remember that these old watches have nothing like gaskets or seals.  Some railroad specs called for swing-out cases for these reasons.

This is an 18 size, 17 jewel movement, made about 1911.