$350-$450 depending on condition
500
$399.00 on gunbroker
519
grades are not marked, the date code is on the left side of the barrel near receiver (see link) those marks are inspector marks. I believe the only want you tell the grade of a 511 is the sights.
Serial numbers were not required before 1968. If it has one, it will be on the barrel/receiver.
$225-$250
150-200 dollars.
You will have to check the on line auction sites to see what they are bringing.
No
511 x 5
50-250 USD
12% of 511 = 12% * 511 = 0.12 * 511 = 61.32