It has been surmised that an extra 1000 guns were brought to the USA in case any replacements needed to be swapped out by the test folks. I think that Tauscher brought in a number, possibly more than a thousand so he could get them in tax free, but that is just a feeling.
Standard Catalog of Lugers - Aarons book is fine, but there are many mistakes in it - I would say a Test Luger falls within or above those values, but would not say that the average 1900 in very nice shape would go for that, not unless a high end dealer.
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Note, holy smokes, you took it completely apart! - I know, lots of folks do that, but I never do unless there is a major issue, but I'm a scrub the barrel, clean the firing pin off type of guy
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when made - about what you guessed, dates are hard to judge...
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