Lion, stars, and crown

5 kopeck Finland stamp, 1860.  Source: Wiki Commons

Grand Duchy of Finland.  After the Napoleonic wars, at the Congress of Vienna in 1815, the European powers settled various territorial and dynastic issues that had arisen during the course of those wars.  As part of this settlement, Finland was separated from Sweden, and awarded to Russia, which was then an absolute monarchy under the tsar.  Finland was governed separately from Russia, most importantly the Tsar was the considered only the Grand Duke of Finland, and as such, rather than an absolute monarch, he was bound by the Finnish constitutional system.

Coat of arms, Grand Duchy of Finland
Source: Wiki commons

Early stamps of Finland displayed no country name.  Identification can be made by the presence of the lion, stars and crown, which were the coat of arms of the grand duchy.  Separation of individual stamps from a printed sheet of multiple stamps was facilitated by serpentine roulette, creating a unique appearance and acting as a further guide to identification.  The stamps were denominated in kopecks, which unlike Russian stamps of the period, were shown in Roman rather than in Cyrillic letters.

Double-headed eagle (Почтовая марка)

Source: Wiki Commons                                        

Russia or Finland.  Used on stamps of Russia before 1917.  Often the eagle is embossed.  Stamps intended for use in Russia will denominated in kopeck (копейка) and ruble (рубль).  Почтовая марка ("postage stamp") will generally appear at the top of the design.  No country name appears on the stamps.

Deutches Reich

Germany, 100pf stamp issued 1934, showing Paul von Hindenburg.
Source: Wiki commons

Germany. Deutsches Reich was an endonym used on German stamps from 1902 to 1945.  

The name is often displayed in the old-fashioned Fractur font, which present difficulty for modern readers, in particular the use of the long, or descending s (ſ), which looks much like the letter f. 

After the defeat of Germany in 1945, Deutsches Reich ceased to be used due to strong association of the word reich with the Nazi regime.

Reichspost

Source: Wiki Commons                           

Germany.  Reichspost is seen only on stamps issued in 1900 and 1901.  These stamps are denominated in penny (Pfennig) and mark.  Stamps below 1 mark in value always include an effigy of Germania, symbolizing the newly-united German nation.

Freistaat Bayern

Source: Wiki commons                                                                  

Bavaria.  The Kingdom of Bavaria, once an independent country, was incorporated into the German Empire in 1871 after the victory in the Franco-Prussian war.  The Kingdom continued in existence under the long-ruling Wittelsbach dynasty, and was permitted, among other things, to issue its own postage stamps.

With the defeat of Germany in 1918, Bavaria ceased to be a monarchy.  Several rival successor regimes then struggled for control.  Freistaat Bayern was the name of one of those rival governments.

Freistaat Bayern exists solely as an overprint on stamps of Germany and the Kingdom of Bavaria.