Well no serial numbers mean that it is not authorized from jl audio which makes sense because they do not authorize internet sales. People take off the serial numbers so jl audio cannot trace where it came from and cancel the account. You will not be able to get jl to fix the amp if you have a problem. That great deal is a double edged sword. You pay less for it but its more of an under the table deal. The used one had a serial number because it was probalby origonally bought from an authorized dealer.

Also periods are a good thing.