I should probably stay out of this , however...
As far as I know rare and very rare have no TCA definition as they apply to Gilbert trains so they are just relative informational descriptors. I did take a look at my often used Centennial Edition guide and see the 25052 was rated a 3 on the 1 to 5P scale. Similar to a 315, 405 and a 982.
Here is where I have to thank Bob Bubeck, and Dave Garrigues for taking the time to publish that guide with rarity estimates 15 rears ago. I never met Bob but have met Dave and many years ago met and discussed Gilbert collecting with Andy Jugle. It was very humbling to find out what I did not know I did not know about Gilbert trains, variations and observed rarity.