This small WWI-era Austro-Hungarian coin represents the 2nd denomination coin of the Krone (Karl I). This coin was preceded by the bronze 2 Heller (Franz Joseph I), which circulated from 1892-1915. It's circulation was relatively short, spanning the mid-late war, from 1916-1918. End with the war's end and the dissolution of the Austro-Hungarian Empire.
The coin is a plain-edged design, made of iron and weights 2.7 g. Its dimensions are 17 mm (0.67 in) wide and 1.5 mm (0.059 in) thick. Making it slightly smaller than a US Penny, in that respect. The previous 2 Heller (Franz Joseph I) was slightly larger, at 19 mm (0.075 in) wide.
Observe
The observe lists the coin's "2" Heller value and mint date (1917), wreathed by oak leaves. Notably the previous 2 Heller (Franz Joseph I) featured a different design. With a single thin oak branch separating the number "2" and coin's mint date. Additionally they featured beading along their rim, unlike the later iron coins.
Both 2 Heller types appear to have been engraved by Anton Scharf, Andreas Neudeck.
Reverse
The reverse features the Austrian-Hungarian Coat of Arms, a double-headed Imperial Eagle overlaid by a Habsburg-Lorraine Shield. The version depicted is an Austrian type, known as the "small coat of arms". This simplified variant was used from 1915-1918.
Similar to the observe, the reverse lacks the beading seen on earlier coins. Instead featuring only a shallow beveled rim.
Additional Notes
The Austro-Hungarian Empire (1867-1918) was a dual constitutional monarchy, formed from the joining of the Austrian and Hungarian Empires.
Austro-Hungary issued dual Austrian and Hungarian currency, which was equal in value.
The Austro-Hungarian Krone/Korona was subdivided into 100 Heller/Fillér.
The dissolution of Austro-Hungary led to the formation of a number of constitutional republics, in the form of Austria, Czechoslovakia, and Poland.
Austro-Hungary monarchal successors were the kingdoms of Hungary and Yugoslavia.
The change from bronze to iron was due to wartime debasement, due to material shortages.
Similar mid to late war debasement was experienced, by Imperial German coinage.