Known as King George V (or KGV) heads, these stamps are highly collectable. Some are very common and some are worth a fortune.
The two you show are not likely to be worth a lot unless there are some plate flaws or watermark variations.
Some of the KGV plate flaws for various issues can be worth hundreds or even thousands of dollars.
Philatelists that have many of these stamps use the
ACSC KGV CATALOGUE - 2018 AUSTRALIAN COMMONWEALTH SPECIALISTS' CATALOGUE
to identify the valuable ones.
You would need to upload higher resolution scans for experts to be able to check your stamps.
The town on your first stamp is Yalgoo, Western Australia. Information on the town can be found here:
https://en.wikipedia.org/wiki/Yalgo...rn_AustraliaThe post office opened around 1894 and complete strikes of the postmark are available on the PPA site for $3-$10.