The Fourth Bureau issue, as some collectors refer to them, is the series of definitive stamps starting in 1922 printed by the Bureau of Engraving and Printing. It starts with catalog #551 and ends with Scott #701. Most of these issues are easily identified. However, the 2¢ issue, with Washington’s head, is the more difficult one to identify.
It’s not as bad as you think. Here is my cheat sheet for identifying these stamps. There are 14 distinct catalog numbers.
There are two types of this stamp. Type I has thin hair lines at the top of Washington’s head. Type II has three very heavy lines of hair at the top of Washington’s head. You don’t need a magnifier to see the difference. It’s very prominent.
|579||I||Rotary||11 x 10||Scarce, produced from coil waste|
|599||I||Rotary||10 vertically||Coil issue|
|599A||II||Rotary||10 vertically||Coil issue|
|606||I||Rotary||10 horizontally||Coil issue|
|634||I||Rotary||11 x 10.5|
|634A||II||Rotary||11 x 10.5|
|646||I||Rotary||11 x 10.5||Overprinted “Molly Pitcher”|
|647||I||Rotary||11 x 10.5||Overprinted “Hawaii”|
|660||I||Rotary||11 x 10.5||Overprinted “Kans”|
|671||I||Rotary||11 x 10.5||Overprinted “Nebr”|
If you are lucky, you may find a #595 masquerading as a #554 in a collection someday.
One more thing to mention. If you can find a joint line pair of #599 and #599A together, it is worth substantially more than when both stamps are either #599 or #599A.
Type II copies are worth more than the Type I copies. The difference in catalog value is about a factor of 300. For example, a MNH line pair of #599 catalogs $4.50. A MNH line pair of #599A is $1150. Type II copies are uncommon, but not scarce. For someone with a little patience, looking through an accumulation of these stamps could prove rewarding if you are able to spot a few Type II stamps in the mix.