New Caledonia 1859 10c black

 1500 were issued. 

This stamp was seldom used and some specialists question if it was used.
Many forgeries exist. Genuine stamps were printed with black separating lines, and thus only the outside borders can have white margins. 
There are 50 different types of this stamp, so it can easily be identified on the full sheet.

Genuine

This is the original sheet

Position 6

Postion 43

Forgeries

Forgeries have too many white margins

Moens Forgeries

Moens 1864 catalog impressions

Many forgeries were paterned after Moens.

Reprints

Note the title in English instead of French

Albania 1913-1920

 The early stamps of Albania can be quite complicated to ID given the variation of handstamps.

Genuine June 1913 Sc4-11 issues

The key features

In clear impressions the pupil of the eyes are evident

In the genuine, the S has flat top & bottom

Here are various genuine issues

Another way to id genuine issues is by the feet.

Forgeries

The top 2 were sold by Fournier

Nov. 1913 Sc27-33

Forgeries

These were sold by Fournier.

1920 Sc113-120

Genuine Issues

Forgeries

These were sold by Fournier

In the genuine top, the S has a rounded top.

Note discrepancies in other letters and spacing.

Fournier - Stamp Forgery Equipment

In 1917 Fournier purchased all the stock from Mercier (actually Henri Goegg).

Included was equipment to produce stamps. With these and over 100 cliches ( see Blog Francois Fournier - King of Forgers).

https://stampforgeries.blogspot.com/search?q=fournier+king

Fournier was able to continue producing and modifying forgeries. These are photos of this equipment at the Geneva Museum.