Two days ago this book was first mentioned here as an essential reference for all US Scott-listed revenue collectors. Here is a small sample of the research and work in this book, accompanied by images of stamps I provide. The original book only has black and white images of some of the stamps referred to in the text.
Chapter XXXVIII of the book concerns the initial 1898 revenues, the surcharged stamps.
R154 Surchaged in Roman Capitals
Cancelled by Wells Fargo
The 1c green postage stamp was first surchaged I.R. in block capitals [R153] 6 1/2 mm. high and 314,890 were issued, all in June, 1898. After the overprinting had been going on for two days and one night [sic] the surcharge was changed to Roman capitals 9 mm. high [as above]. Both surcharges are in red and the latter one occurs inverted.
The 2c carmine postage stamp was surchaged only with 9mm. Roman type and occurs both normal and inverted. The surcharge is dark blue.
On both the 1c and 2c with the larger surcharge a small period after the "I" occurs four times on each pane of 100 stamps. It is always the 41st, 46th, 91st, and 96th stamp on the pane--that is, the first stamp in the bottom row of each quarter pane. It is thought that this is a secret or control mark placed there intentionally.
Small period after the I
The Boston Book states that 63,300,000 of the 1c and 62,000,000 of the 2c, all with the 9 mm. surcharge, were issued, all in June, 1898. The Bureau reports differ somewhat from these figures, giving the total of 1c stamps with both surcharges delivered up to June 30, 1898 as 42,000,000 and 20,800,000 after June 30, 1898, or 62,800,000 of the 1c in all. Their record of the surcharged 2c stamps delivered is 32,000,000 up to June 30, 1898, and 23,600,000 thereafter, which totals to 61,600,000. Obviously the Internal Revenue office did not deliver more surcharged stamps than were printed and delivered to them by the Bureau of Engraving and Printing.