Not sure I would say all pre-1930 based on what I'm seeing in the photo.
The yellow on the lower left edge, the purply flamey in the upper right quadrant, the red and white in the very center [edit: that's a transitional, isn't it], and the aqua and white on the bottom left, make me consider pushing this into the 30's. Or at least I'd like to look more closely at them.
The "less old-looking corkscrews" are a wild-card. They need to be considered.