How many Scouts on Stamps collectors are aware of the fakes that may be resting in your collection for the Zumstein 1-2, overprints 3-4 (Gibbons 1-2)?  The extremely rare overprints "Prijezd Presidenta Masryka" (meaning arrival of President Masaryk), which appears diagonally on the stamps, have sold at very high prices.  The phonies of these stamps appear both as fake stamps with fake overprints and as genuine stamps with fake overprints.

How can we detect the fakes?  On the genuine 10h value (blue), the foot of the lion on the left side of the stamp has four toes long and thin.  On the 10h fake, that same foot has four toes short and thick.  On the 20h value (red), the situation is just the reverse; the genuine has the short thick toes, while the fake has thin toes.

Other fakes of these stamps have appeared with varying differences from the real ones.  Genuine stamps have three horizontal lines, on both sides of the word "Posta" at the top of the stamp, all of equal width.  On the fakes, the middle line is longer.

Stamps with "pin hole" perforations are outright forgeries, but most fakes appear with the regular simulated perfs.  The fakes of these stamps has been characterized as rather crude.

The overprint fakes are less of a problem to spot, for how many of us can afford the genuine article?  About 100 genuine mint sets are known, and about 10 or 15 on cover.  Generally, the fake overprint has thinner letters.  The periods above the letters "i" and "j" are distinct and the centers of the letters "d" and "e" are plain on the fakes.  The genuine overprint has heavier letters, the periods often run into the letters themselves, and the centers referred to above are usually closed or nearly so.

Don't rely on this article alone.  When expending money on valuable stamps, be sure to have the items expertized.  Proof copies in different colors are known and believed to be genuine, but such proofs are expensive.