The character 虎 as appeared on the poster is written in cursive script (or cursory style). I think cursive script is a modern thing, not exactly related to archaic characters. And people today still write a cursive character in many different ways.
Here are some examples of cursive and other scripts, two of which are 虎 in cursive form near the middle of the page: [www.google.com.hk]
Here are some examples of cursive and other scripts, two of which are 虎 in cursive form near the middle of the page: [www.google.com.hk]