First of all, could you please add a picture to this subject showing the actual makers mark on it? Star with number inside indicated the particular plant it was made at.
Trenton Potteries specialized in bathroom pieces (tubs, toilets, etc) aka sanitary ware. It also was prominent in making items for bathroom use. This could be a fancy soap dish!
HOWEVER, they also made items for apothecary/pharmaceutical use.....and if the depression is round and shows some wear inside....it could be a fancy part of a mortar/pestle. (My personal favorite....)
HOWEVER.......later they did make items for the kitchen....and though not your typical style....this could very well be an ornate egg server! So, does an egg fit in the depression well?
AND they also made items for floral usage....
Plant number can help....