This Crystal Ball article III by Mark Nye indicates that you have a #1917 Plainware Butter Dish. Minus the lid, it is a lemon dish. The tab-handled tub had a long history as a covered butter dish with various decorations and covers and finials. It ended in the 30s with the design you have. Near the bottom of the page in the article, is a hazy image of 5 or 6 covered butter dishes. In the middle of the bottom row is what looks like your little 5" covered butter. If you want more info, read all 3 of these excellent Crystal Ball articles on Cambridge butter dishes.
