I somehow managed to accidentally acquire one of his offspring. The mom was a bantam sized light brown hen with a single comb, and I didn't think to take a picture of her. But, this guy is definitely dad.
Sorry, my picture was really iffy, and I don't see it getting better anytime soon. He was donated to a local feed store a while back. About a month ago, someone dumped a few hens behind the store in the middle of the night. The rooster would come inside, but the hens were really skittish. A couple days ago, they realized the hens had hatched a bunch of chicks. They were worried about critters getting the babies, so when I was in getting feed last night, I offered to catch everyone and bring them inside. I kept one of the chicks, and another customer took a bunch more. Anyway, I was in a rush to leave because my "quick trip" to the feed store turned into a much bigger adventure than anticipated.
I googled both Blue Marans and Blue Langshan, and I feel about 95% confident the rooster is a Blue Langshan. The chick I adopted is a dead ringer for a langshan as well, except she's smaller (bantam mom at work there) and the leg feathering is so minimal I suspect she'll be clean legged as an adult.