If these are true mono tracks with ONE channel, then you can look at the [channels] field. If it's 1, it's mono. A value of 2 would be stereo.
If these are "dual mono" tracks where L and R are identical, then that's much harder. I'm not sure how you'd do that without some external tool that did something like computing a checksum of each channel and then comparing them to see if they were the same.
Don't most early recordings in mono usually indicate that on the album cover, and/or album name? Like early Beatles stuff that was mono.
Brian.