Onion, Tomato Slicing Guide, Vintage Longner Mfg. Hostess Slicing Guide Tool, Bakelite Handle (HG-A172)
 
This tool is a vintage onion, tomato, or cheese slicer/holder, also known as a produce slicing guide. It is a kitchen gadget used to hold fruits, vegetables, or cheese in place while slicing them.
This particular tool features:
A handle made of a vintage material, called Bakelite, which has a marbled, tortoise-shell-like appearance. 
Multiple stainless steel prongs that are pointed and sharp, designed to pierce and hold the food item securely. 

Condition- Great