The Gasplane shown is one of the most common found examples today. It dates from March 1944 and has the usual characteristics for tropical & arctic examples; the Tp\Ark designation and the grey squares where the user should hold it.
Many of these have identical manufacturing markings. Apart from March 1944 I have also seen them with April 1944 dates. If you have a similar example with a different date I would love to hear from you.
Also shown is the very high quality 1940 dated pouch it came with.
You may also be interested in this page which shows a tropical gasplane entry in a Soldbuch.