"Lunch Box Specials" are those firearms whose origin can be (or perhaps can't be) traced to parts that were surreptitiously removed from a factory in worker's lunch boxes, and assembled outside of the factory and without the factory's knowledge...
In some cases, these firearms have no markings whatsoever... one of the websites dedicated to the M1911 has photo examples of such guns... and I have seen photos of at least one Luger that had never been serial numbered or factory marked...
How they got out of the factory will always be a mystery...