Maybe I’m not looking closely enough, but Maraschino cherries seem to be pitless without showing signs of being pitted when served at restaurants, for example. Are they seedless cherries, perhaps? anyone have the “inside” scoop on this?
No pun intended 
I would guess they’re pitted cleverly, and/or perhaps the opening “heals” a bit during marination.
From http://www.allrecipes.com/encyc/terms/m/7369.asp:
This specially treated fruit can be made from any variety of cherry, though the ROYAL ANN is most often used. The cherries are pitted and then MACERATED in a flavored SUGAR SYRUP (usually almond flavor for red cherries, mint for green). At one time they were traditionally
flavored with MARASCHINO LIQUEUR, though such an extravagance is now
rare. The cherries are then dyed red or green. The federal government has now banned the use of the harmful dyes that were used until recently. Maraschino cherries can be purchased with or without stems. They’re used as a garnish for desserts and cocktails, as well as in baked goods and fruit salads.
They are most definitely pitted…if you cut one in half you can see the little cavern where the pit used to be.
Well, I guess it’s because their parents were killed, and they ended up being raised by pirates, and you know pirates aren’t exactly good with kids … oh, wait, I thought you wanted to know why they’re PITILESS. Big difference.
Cherries can be pitted by poking with a nail, or other cylindrical object. The pit is forced out through the skin on the opposite side. If you look at your marischinos closely, you should see a small entry wound on one side, and a somewhat larger exit wound on the opposite side. With pie cherries it’s easiest to poke the nail in at the spot where the stem was, and force the pit out the other end, but with marischinos, they want to keep the stem, so the holes are on the side of the cherries.
We had a discussion on marachino cherries and their manufacture in this thread: