I believe the Mint spec for a new silver quarter 1873 - 1947 was 6.25 grams +/- .097 grams. (I don't remember where I found this) ... but, say 6.153 to 6.347 grams.
Factoring in your scale calibration tolerance/accuracy, Mint tolerance, and circulation wear, my opinion is that 6.04 grams is not too far out of tolerance. At the low end: (6.153 - 6.04 = 0.113 grams) = approximately 1.8% underweight (if my information and calculations are correct).

























