It wouldn't be my choice, the original GM5 only discs out small iron and there's no number ID, the latest GM5+ can disc or tone break to any point on the scale, it has a number ID, better audio, but no notch.
Nice fast machine, fairly deep, it alerts you to targets better than most, finds really small stuff in 18khz.
Be sure you buy from an approved GM dealer or GM might not honour the warranty.