Well this one is marked sold, but they don't say who manufactures it either.
I just says limited production, it may have been a garage kit.
Hopefully someone will see it here and help you out.
You might try posting at the Edina model Yacht club forums.
The city built them three pond, and they have a fairly bit club base.
Maybe someone there will recognize the Thorax. One of their members, GeorgeP posts at "RCgroups.com".
Here is the retailer image and info
Thorax Anchor Handling Tug
1/48 scale
Complete with Plans and Pictures
Limited Production –No longer being produced anywhere.
Complete as pictured with Z-drives, motors, speed controllers, and universals.
(List Price: $ 249.00)
Buy Now For Only: $ 189.00!!SOLD!!
Maybe if you contact the retailer they can tell you where it came from, and
then you may be able to find some plans or documentation.
http://www.loyalhannadockyard.com/Limited.htm