Hello. Not a double die. Looks like rippled coin or Die deterioration doubling.

Very nice. Thanks for sharing.

Not just if we can call this a DDR. Not in Renniks Pre-Decimal Coin Varieties catalogue.

Here's one similar to yours

Hello. Depends on the grade. Various real sales can be found here:
https://www.coinsandaustralia.com/coins ... end=Search

Can you post pictures to show us the coin? Will be easier to identify.

Probably not much unless certified by PCGS or PMG. Sequential doesn't add value for modern notes.

Sequential for modern banknotes doesn't add value.

Modern banknotes, except if in EXCELLENT condition and/or with specific serial number, aren't generally worth more than face value.

Hello and welcome!

Here's more information on what you got:
https://www.coinsandaustralia.com/coins ... =cuds&id=3

Hello!

Could you post some pictures? Will be easier to help. Most $50 banknotes are worth face value unless rare serial or in pristine condition,

https://www.coinsandaustralia.com/bankn ... ecimal.php

Picture didn't work. Reply to this and use the Attachements tab under your message. It should upload correctly.