Mining Sleuce with Riffle Base

This was on the verge for most of January 2020. First dumped outside the North Annandale, then migrating to the Annandale Shops. On 23 January, I finally succumbed and took it home. 
Puzzled by what it was, I sought the help of the facebook group StreetbountyInnerWest

The group came up with four leads.
  1. Part of a Beehive
  2. Washing Board
  3. Roof Vent (eg in a Gable)
  4. Mining Sleuce
With these leads this object would appear to be a Mining Sleuce Box with Riffles to strain the gold.
"After the soil of a hillside was turned into a slurry with water, it waschannelled down the hill into sluice boxes, where minerals were caught on “riffles” in the boxes."...

More at:

Gold Mining Links to Annandale