As far as I'm aware, most companies don't give any such indicator as to what a rods action might be. The exception being Shimano, which uses "FA" to indicate a Fast Actioned rod.
Drennan are prone to giving a full written description as part of the rod graphics.
Most specialist and carp rods use test curve (TC) ratings, usually stated in pounds/ounces. However, such a rating gives no hint of what the action might be.
There's a pic of differing actions
here.
However, to confuse matters further, other terms are also used. A slow actioned rod might also be called a through action. A fast actioned rod described as having a tip action. You'll also see terms such as "parabolic actioned". I'm well aware of what a parabola is, how it really relates to a fishing rod action is quite beyond me. I accept that it seems to mean something to many, but it seems to be a bit of marketing BS to me.
Here's a
link or
two explaining test curves. As far as I'm concerned, it's a deeply flawed way of indicating the capability of a rod as it gives no indication of an action.