silurus microdorsalis

I’m about to purchase a golden “wels” catfish but the current owner is unsure on it’s particular species at first I thought it was s. meridionalis but now I’m unsure does anyone have any ways of correctly identifying them so I know whether I’m going to end up with a 3ft or a 10ft fish eventually

https://www.planetcatfish.com/common/species.php?species_id=5654 They look like micro sized wels. I wonder if @fugupuff can get some They have a very thorough pcf entry for a species with 0 registered keepers, weird.