Can anyone ID this Tremec?

I can't tell if it's a 3550 or a 600

If it's a TKO it'll have a 31 spline output shaft


If it's a 3550 it'll have a 28 spline output shaft


Is the Tremec ID code/production TAG present?

It's for Fords.

https://www.summitracing.com/parts/cmg-tcet5008

Thanks for the replies.
It's the 31 spline version.
Will look for production tag.