What a fantastic donation!  This horse blanket is a Roustabout T. C. LT WT Cool Plus.  It's a beautiful Hunter green color with tan trim, and sports a fleece collar for extra warmth and softness. 

It's also waterproof, is an 84" blanket, and appears to be new, or if ever used is in new condition.  It comes in a zippered bag for protection.

Main photo is from the website.  There's also a matching hood available from Kensington for this blanket.

Here's what the Kensington website has to say:

"The sleek and fitted Traditional Cut light weight
Roustabout Turnout is made of a 600 x 1200 Denier
Ripstop outer shell for flexibility and strength.
Breathable (5000g/24mva) waterproof (4000 mm)
Teflon® coated outer shell with super absorbent
Coolwick® liner with 180g of hollow fiberfill. Includes
a single 2” belly strap with snaps and D’s, detachable
elastic leg straps for added durability, D-rings for the
optional Hood (8533RLT) and a removable tail piece.
Ideal in cold climates and providing warmth in
temperatures down into the low 20’s and in warm
climates up to high 60’s. This turnout is great for
slow cool downs and lots of rain. Now with shoulder
gussets, tail flap, and removalbe belly band."