I cannot explain my fascination with the Marmon-Herrington tanks. I realize they were far from being "great" tanks. However, as you stated, the Dutch and the Latin American countries that used them felt they were tough and reliable vehicles. The U.S. troops had a different opinion from what I have read though.
This can be attributed to the fact that U.S. soldiers had access to tanks produced with government backing. Marmon-Herrington set out to sell tanks as a commercial venture, using their own assets and designs. In a sense, you could say that Marmon-Herrington was the United States' "Skoda" (although Skoda tanks had a much more glorious history).
Locating information and photos on these tanks is a task in itself. If you are not familiar with them in the first place, finding information is even that much more difficult. To this day I cannot keep the various nomenclatures of the "normal" WWII tanks straight (not always at least). However, by some quirk of nature, I am able to cite the nomenclature used by Marmon-Herrington on thier "tanks".
Don't ask me where they came up with those names. Some of them, like the CTL series are easy (Combat Tank, Light), but what the heck does CTMS-1TBI and MTLS-1GI4 mean?!
As for the tank in Guatemala you spoke about, I've seen a photo of it on the internet (but can't for the life of me remember where).