I would certainly NOT melt them down. I have never seen any like them. I am not a true collector - but I do have about 80 decoy anchors hanging from the ceiling in my shop - almost all of which my Dad and I have accumulated over our lifetimes.
Most are homemade - a big part of the charm for me - but I have a bunch of factory anchors as well. This mushroom-style was made by D. C. Sanford - in Bridgeport, CT. It has most of the same properties as yours:
How heavy are they? They look like a nice design for low energy waters. For example, I use 3-ounce pyramid or bank sinkers on the rigs I use in beaver ponds and the like - and I have some very light mushrooms as well.
I recommend you enjoy them for what they are. You can use them for small-water rigs - or simply hang one from you shop ceiling.
BTW: I just a couple dozen anchors to a friend. They looked just like your Greenhawk anchors - but had no ID cast ino them. I'll see if I have a photo to share.