Your rifle is not a Z series, the Z's had a prefix, not a suffix. Also the Z prefix rifles started right around 4,000,000 and ended right around Z4,002,920. They only made 28 to 2900 of them. Your number is way too high to be a Z, but I will bet that your last digit is a 7 and that would make it early in the final production run of A4s. Still made in Feb of 44 though.