1910 T218 Boxing card question
 

Okay, guys, I don't know much about boxing card at all, but I have a large group of mostly T218 boxing cards like the ones pictured and a few T220.

The first question, on the back, just above Mecca around half have listed series #2 51 to 100, the others do not. Are these different printings? Is one more valuable than the other?

Next, I can see some of these on eBay to get an idea, but only for the same condition cards. I have a Beckett account for the vintage cards, but they all list N/A even for these older cards that seem to have plenty of sales looking at the past year. Is there somewhere else you recommend to get an idea of value for these?

And last, since I don't know a lot about boxing, besides Jack Johnson, who else is in these two sets that I should be looking out for?

Again, thanks in advance for your help and guidance!