DLyons Oct 25, 2012:

I think there are cases (e.g. doing manual input of barcodes at a checkout) when one wants to bypass checking.

Didier Fourcot Oct 25, 2012:

@DLyons I have considered the option of "pass through" but what's the point of a check digit that does not check anything?
Also the fact is there IS a check digit in most barcode systems and it is used, so this is the possible understanding I saw, but I don't mean that it is the only possible understanding

DLyons Oct 25, 2012:

I haven't seen any usage of "through" like this before. As a pure guess, I'd say it means "pass through" i.e. without any calculation/check being carried out.

What Didier suggests below may be correct, but his site doesn't give any evidence either for or against that suggestion.