The device is a 2R20, of which there was only one used at Parramatta. Any differences claimed by Freeman are easily attributed to wear.
I have four on DLR stamps (which should come as no surprise) but also have 2 examples on cover, both bearing 2d imperf diadems. The nicer of the two strikes is below, although the cover leaves a great deal to be desired.


Plenty on Trove about the addressee, which is probably this man
https://trove.nla.gov.au/search/cat...&l-year=1875