Hello all--happy holiday season!

Been a few weeks since last question so hopefully you will have patience with me again now. 

Have acquired a box from a guy that is changing from HO to N scale--lots of odds and end, track, rolling stock, and about 8 locos. He said some were DCC and some DC and some ran and others didn't --my question --is there any way to tell the difference. between the two systems?  Maybe marking of some sort?

I have a Bachman controller the will accommodate  DCC and one pad for DC, Am trying them on both systems and some work fine--others--nope. Would like to know which is which tho..

Also--I understand that a DC should not be on a DCC track when powered--is that correct ?? Is there a power difference?

Thanks all---