I bought these as a box full from a dealer in my neck of the woods, finding them quite lovely things, at least a handful of them frame-worthy and others perhaps fodder for other things. I believe they were/are practice efforts in advance of making theorem paintings or decorating tinware (tole painting) and incorporate a combination of painting done with stencils and by hand. Executed in a mix of metallics and color on black card/board with a sheen to it.
Average size (first one for example) @ 9 1/4 x 11 1/2. All in very good condition, 20th rather than 19th c I believe. Price is for the lot--all pictured.