With an Erfurt, it's not just matching numbers, but also most of the parts (including the grip screws) are marked with acceptance marks.
There was an old reference to normally numbered parts in this discussion:
http://www.thehighroad.org/archive/i.../t-318955.html
Also, to be collectable, it should have 80% or better original rust blued finish and strawing. 80% is usually considered the minimum.
If you can post photographs here, members are likely to be able to help as well...
Marc
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Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.