I just got a 5.75 concentric for my Tejon and it has become a major coin/jewelry hunter for parks. Problem is, the thing hits DEEP on pull tabs of both kinds as well as aluminum, but you have to dig them to get the gold.
If you want to just coin hunt, set the first disrcim to break up on foil, set the second to break up on a nickle. You will get lots of depth due to the main discrim being very low. When you get a solid hit, switch to the alt discrim. If its still solid, dig it...its probably a coin ( or something round that fooled it).
If the alt discrim is breaking up the target, it may be nickle, pull tab or gold.
For me, since the pin pointing is dead on, I dig everything in a park from foil on up. You never know when the gold chain or small diamond ring will show up.
BUT...get the small coil. You will never take it off.
One other thing..I seldom set my sensitivity higher than 7 on my Tejon for this type of hunting. It's deep enough and stable at this setting.