Block Optic is a glass pattern manufactured by Hocking Glass in 1929 -- 1933.  However, I have seen listed on eBay many patterns identified as Block Optic that were made by other companies. 

No matter what you see listed as a center-handled Sandwich Server, Block Optic never made one.  I have researched reprints of original ads and have never seen a sandwich server that was made by Hocking in this pattern.

If the glass has a narrow border of tiny dots, it was made by L. E. Smith, their Homestead pattern. 

Liberty made sandwich servers with two styles of handles in their Bamboo Optic pattern.  Both of these handles can be verified by reprints of the old ads found in currently available Depression glass books. 

Don't be fooled, do your research!