Mid century cylinder planter Grubb

I recently purchased some mid century cylinder planters that are in exc condition with textured ribbing. The bottoms of them show Grubb as the maker. The only info I could find was a Grubb Pottery and Manufacturing in Marshall, Tx. Can anyone confirm this? In addition, I don’t know how many of these cylinder planters were made and if they are considered to be highly collectible, so any additional thoughts or comments are welcome. I plan on purchasing two more cylinder planters that are even bigger.