I'm not going to be a great deal of help with dating your Muir Woods. You are correct in that not much has been posted about them. Maybe you found my couple of threads or posts? Here are a couple of pictures of the one I found at the dump.

I don't really care for MTB flat bars, etc., so I thought I'd have some fun with mine. I ended up giving it to a 15 year old neighbor. He thinks it's pretty "wicked" as they say here in NH. I'm amazed at how different your's is painted and decaled. I don't know the serial number at the moment, but I can check later today.





The condition when I retrieved it from the dump.