National Bohemian question

[dtsoc]

I rolled this from a flat sheet at least ten years ago. It was lidless until I finally figured out how to lid it, without soldiering the inside seam. Anyway, I thought I'd look it up in the USBC book. It appears to be a dark seam, but with the regular width band. I don't see it pictured. Doubt it's rare, but it may have been a test sheet. I picked it up in a high end group of soda sheets, including some test cans. Anyone have any more info?
Dave T

[Rockbob]

I don't think its a test sheet. I have the same can both in a zip and a fan tab. Both cans have the NB-313 marking at the seam. Besides the different tops, the fan tab has a darker stamp above the chevron.

[dtsoc]

Thanks for the input. Appreciate it.
Dave