I have two prints by C. M. Coolidge produced by Edward Gross C. Inc. Post Mortem & Sitting Up With A Sick Friend. I was wondering how much they were worth or were I could go to find out much they were worth.

No idea if this is anything like the style of the prints you have but It is by Edward Gross Co.

Vintage Print EDWARD GROSS CO. " Fritz & Ursula " NICE - eBay (item 380123899015 end time May-19-09 15:08:11 PDT) (http://cgi.ebay.com/Vintage-Print-EDWARD-GROSS-CO.-%22-Fritz-&-Ursula-%22-NICE_W0QQitemZ380123899015QQcmdZViewItemQQimsxZ200 90513?IMSfp=TL090513129006r7829)

And these are C M Coolidge prints

http://www.globalgallery.net/search.php?af=c.m.+coolidge

I can't seem to find the two togther sorry...

I have a print by edward gross dated 1906,Chicago. Copywright #3307 (or 3309 no super clear)
It is a print of men robbing a couple. Wondering how to find out what it's worth?