Herb,
The early commercial slides were marked "calibre". The newest commercial I have owned was a 1915 vintage marked as such.
As a 'generalist' collector, I'll admit my knowledge is rather shallow, but fairly broad with spikes here and there (1st and 2nd delivery 1911's up to ser# 25,000, for instance), and I've even owned a few early civilians.
In my experience where 1911 and Luger collectors differ is in the definitions of "Correct", "Right" and "restoration'. I don't know many 1911 people that would lose sleep over swapping out a barrel or even an entire sub assembly, as long as the finish/wear matched. As few parts were numbered on 1911s and spare parts remain plentiful, this luxury of "correctness" is not available to Luger collectors.
Here is ser# 24212, I recently sold on GB. It was perhaps the most 'correct' 1911 I have owned to date and was documented through springfield research service.
http://img134.imageshack.us/img134/1003/dsc000953ef.jpg