Looking a little closer and also in older index files i found this. 
*****A "C" Following a Project Gutenberg eBook Number Indicates Copyri
+ght****
*****A "*" Following a Project Gutenberg eBook Number Indicates Reserv
+ed ****


[snip]

The Life of John Ruskin, by W. G. Collingwood                         
+   13076
A Hero and a Great Man, by Francis Kruckvich                          
+   13075C
  [Illustrator: Fritz]

Punch, Vol. 100, February 7, 1891, Ed. by Sir Francis Burnand         
+   13074

[snip]

Feb 1995 Moon and Sixpence by Somerset Maugham [Maugham #1][moonaxxx.x
+xx]  222
Feb 1995 The Return of Sherlock Holmes [Magazine Edition]  [rholmxxb.x
+xx]  221B
Feb 1995 The Secret Sharer, by Joseph Conrad [Conrad #2]   [ssharxxx.x
+xx]  220

[download]
I did not found the meaning of the 'B' though.

In reply to Re^2: Parsing Gutenberg Catalog Index by lidden
in thread Parsing Gutenberg Catalog Index by hacker

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