The Upper Silesia plebiscite territory began issuing official stamps in 1920. In April 1920 the German Local Official Stamps for the State of Prussia were overprinted "C.G.H.S." for government use in the plebiscite territory. C.G.H.S. stands for the French: Commission de Gouvernement Haute Silesie.
The standard orientation of these overprints is either horizontal or vertical ... Michel Types I-IV shown below. These overprint varieties all sell for the normal catalog values.
Beginning in July 1920 and continuing through February 1922, the government of the Upper Silesia plebiscite territory overprinted the contemporary Weimar German Official stamps with the same "C.G.H.S." overprints (Mi. Dienstmarken #8-20, Sc. #O39-51).
The 2 Mk. denomination comes in two different varieties, the first being watermarked lozenges (1920) and the second being watermarked network (1922). The lozenge watermark is the higher priced of the two. The rest of the stamps in the series are watermarked lozenges.
The Michel Deutschland-Spezial-Katalog lists 20 different orientation types for these overprints! Types V-XX do have a premium of 25% to 100%
Michel Type I: Overprint Upright, from the top.
Michel Type II: Overprint Upright, from the bottom.
Michel Type III: Overprint Horizontal, normal orientation.
Michel Type IV: Overprint Horizontal, inverted.
Michel Type V: Overprint Double Upright, from the top.
Michel Type VI: Overprint Double Upright, from the bottom.
Michel Type VII: Overprint Double Upright, Types I & II.
Michel Type VIII: Overprint Double Upright, Types II & I.
Michel Type IX: Overprint Double Horizontal, normal orientation.
Michel Type X: Overprint Double Horizontal, both inverted.
Michel Type XI: Overprint Double Horizontal, Types III & IV.
Michel Type XII: Overprint Double Horizontal, Types IV & III.
Michel Type XIII: Overprint Crossed, Types I & III.
Michel Type XIV: Overprint Crossed, Types I & IV.
Michel Type XV: Overprint Crossed, Types II & III.
Michel Type XVI: Overprint Crossed, Types II & IV.
Michel Type XVII: Overprint Diagonal, upper left to lower right.
Michel Type XVIII: Overprint Diagonal, lower right to upper left.
Michel Type XIX: Overprint Diagonal, lower left to upper right.
Michel Type XX: Overprint Diagonal, upper right to lower left.
The Michel catalog indicates that these Upper Silesia Plebiscite stamps are "speculative" meaning that they were probably intentional printer's creations of the period and NOT actual printing errors. Nevertheless, they are interesting, inexpensive, and they do make an impressive display.
When shopping the internet though, shop around and do not pay high prices for them. Some sellers charge exorbitant prices for these, as errors, and are taking advantage of novice specialists. A little comparison shopping will serve the specialist well and will save a lot of money.