Look at the lifter block The point where the pushrod sits into That cup will have a spring underneath it This is hyd If the pushrod sits in a cup no spring visible then it probably is a solid Does this make sense ?
generally speaking
solid.....adj lifter
hydro.....adj prod
there is a conversion where you can drop a bucket into a hydro, making it solid, but you still use the hydro prod
however...if you see an adj lifter...... it is solid
I can understand that with the conversion kits to change hydraulics to solids it can be a little confusing. But the one feature of the hydraulic that a solid does not have is that once you take the initial play out of the pushrod with a hydraulic you can keep tightening untill the plunger in the hydraulic bottoms out,in fact that is how you start adjusting them.With a solid once you take the initial play out you can not go further without doing damage. This is a for sure way to tell, but this is only for telling them apart if other means fail and do not crank the engine with them over tight.