Tree 310/315?

[Provectus]

Hello all, I'm new to the forum and have already found a wealth of information here, so I would like to start out with a big "Thanks" to all the posters here!!

Now onto my question: I recently bought a Tree 310 its in great shape it looks almost new, I dont know much about this mill, but it has a metal plaque just below the Tree logo on the head marked with 315. this looks like a factory placement and I was wondering if this is common or if this is some sort of a factory upgrade or or or ....?
TIA

[Provectus]

Just thought I would post it here in case anyone was interested, it seems that Tree did offer the 315 upgrade from the 310, and it normaly involved a factory service tech coming out and gutting the 310 head and replacing everything in it including the spidle motor. When he left you had a 5000+ rpm machine with programable speed and brakes. The plate i noticed and was questioning actualy covers the hole where the manual speed control was. Well thats about it, hope this helps somebody out there.