It is an Austrian coin.
Not enough information. What is the coin's denomination? Please post a new question.
There are many places one might go to find a coin price guide. The World Coin Price Guide website is likely the best resource for one researching Austrian coins.
A zehner is a Medieval Austrian coin, worth 10 kreutzers.
A zwanziger was an old Austrian coin of value 20 kreutzers.
Please check your coin again and post a new, separate question with its date and whether the "50" refers to groschen or schilling.
The value of an Austrian 20 corona 1915 coin can vary depending on its condition. As of now, it typically ranges from $300 to $600 for circulated coins and can go up to $1000 or more for coins in better condition. It's recommended to consult with a coin dealer or collector for an accurate valuation.
Before the Euro was introduced in 2002, the currency of Austria was the Austrian Schilling, divided into 100 Gröschen.
Archduke
A coin collection is called, well, a coin collection. The hobby of collecting coins is called numismatics.
It is called the Austria Schilling.
They would be called 'Austrian'. (pronounced 'oss-tree-ann').