SRS Serial Help

[Grabenkater]

I have recently become obsessed with Springfield trapdoors. I've wrangled three in the past month. I picked up a cobbled together carbine made from all original parts and two rifles. I am wondering if someone can trace two serial numbers.

471313

506857

[Tom Trevor]

Nothing on those numbers and the closest are close to one hundred away.

[Grabenkater]

Thanks, Tom!