This can be easily decoded. Note: A welding rod that does not have an "E" on it is classified as oxy-fuel welding rod; not for use with a "stick" or arc welder.
"E" stands for "Electrode"
The first two digits (or first 3 if it's a 5-digit number) are an abbreviation of the weld's strength. To determine the strength of the weld, take the 2 digits, in this case 60, and multiply by 1000 to get the weld strength in PSI.
So, if you had welded two plates together, with the weld covering one square inch (or even 1/4" x 4", that's still one square inch) that weld could take 60,000 pounds of pulling force.
Typical vales are 60, 70, 80, 90, 100, 110....