An "Eddystone" is properly a US Rifle, Caliber 30 of 1917. Value will depend heavily on condition, and whether it has been modified in any way. I paid $800 last year for one in very good original condition.
Google 1917 eddystone, then find the link for us military rifles then type in your serial number you can get the month and year of manufacture of the rifle action. it should be July 1918 for the serial number you provided. don't know much about price. hope this help a little
It is simply the sequence of production. Means it was made after # 300611, and before 300613.
Check: gunboards.com (under buy/sell/trade)
made June 1918
$1000
100-425 USD
The model number is 117
No published sn data.
Impossible to answer without a detailed description
You sure this isn't an EJN 757 instead of a JEN 757? I have a EJN 757 in 3006 and would also be interested in any info. for this rifle.
50-160 USD
About $250, depending on which version and condition.