GB,
I did quickie test between shrew coil and 8x9 concentric on the Cibola
Shrew coil:
Nickel=bottom line of nickels
Zincoln=a&t on discriminate after max line
Penny= a&n on discriminate after max line
Dime=just starts to break at max
Quarter=solid tone at max

8x9 concentric:
Nickel=same
Zincoln=max line
Penny=a&t on discriminate after max line
Dime=n on discriminate after max line
Quarter= same

3d masking under rusty can the 8x9 concentric is able to disc out iron rusty can end and still pick up nickel as broken other coins are diggable tones especially dime and quarter. Shrew masks out on all.

If you have a piece of old rusty sheet metal or old cut nail you can try the following with the Vaquero, set discrimination to just trim out iron, next put a coin below the iron target and you should be able to hear only the coin with the concentric coil. Think I sent ya that crappy video I did done with a half dime and trime with the Tejon. Was able to pick those up >6".

Between the Tejon and the Cibola I personally like the audio on the Tejon better and it has much faster recovery speed but bottom line if your hunting in iron infested sites the Vaquero should do just fine.