Enduro did make a tiny number of those saddlebags for Loops. The only MG Enduros I'm aware of are owned by me. I'd love to hear from anyone else who has a set. The back of the bags are molded to hug the bike, so it's quite apparent when you fit them up to a Guzzi that they were made expressly for a Loop. The BMWs had vertical shocks and the Guzzis had lay down shocks. They are worth silly money for the less common of the BMW Enduros. God knows what MG Enduros might be worth.
Information from Mike Ittner:
There is a site that sells repops of the old BMW Enduro bags called Luxor Marine (Web site no longer exists. Owners name is Mark Yamron.). There is a beemer guy here in town who has a set of original ones on his beautifully restored BMW which he says are worth about USD $1,500.00. He also says he would rather have the repops as they are better than the originals. I know there are some on the list with BMWs so I am just putting this out there. USD $550.00 sounds good by comparison.