Here's an attractive Green Glazed multipart porcelain insulator found in Czechslovakia. Cemented two-piece unit. Manufacturer's mark found: M (large capital letter) FCP (below). This is believed to be a Merklin product. 1 1/4" pinhole.

Measures 6 inches tall x 5 3/8 inches wide on upper shell; 4 5/8 inches wide 2nd shell; 4 1/4 inches wide base shell. Here's how it would be assigned in the book: 5 3/8 - 4 5/8 - 4 1/4 x 6. Looks like it merits the number M-2030. Any feedback on this assignment accepted. Thanks