Thanks for remembering the GWEN J.David!
She is certainly the smallest industrial "full-size" loco I know of. GWEN's brother engine the JACK (almost identical, but 22 years older) should still be in Leeds, England. Searching "GWEN" on the forum would reveal several posts about it.
Here's a photo of your's truly next to my brother's engine at an operating day about 10 years ago. The engine's operating restoration was completed in 1991. It's an interesting outside frame design, with Stephenson valve gear.
Bob of AZ