Germany - Altenbach Solingen Utility Knife

[GlennH]

Recently found this one amongst my dad's knife "collection" (accumulation). I've seen quite a few similar patterns on here, but not many Altenbach knives. Also, not many with the file blade. Any ideas on a date range of production? Are these fairly common, or I have I just not been looking in the right places? A pretty cool little knife, I think.