Should be off a ROD (Railway Operating Division - British War Department) 2-8-0....
North British builder's No. 22145 was ROD 2054 & was later LNER 6289, LNER 3852 & BR 63852.
In other words, one of these....
Attachment:
r8-1488.jpg [ 168.23 KiB | Viewed 2192 times ]
One of them is preserved in the UK (National collection - currently at the GCR) and there are 3 in Australia (One at the Richmond Vale Railway and two at the infamous Dorrigo "museum").
What I did note whilst doing a quick internet search for that plate is that particular builders number does turn up on several searches along with at least one comment that its a "Replica Plate", so there may be a few of them out there!