With 3 rough sides and 1 smooth, it appears that it went inset in a structure/cabinet. This reminds me of the earlier earthen sinks that were used for laundry/scrubbing. Shallow on the end for hand kneading, yet angled to let water drain easily. HOWEVER...i do recall a much longer version of a sink similar to this in The Winchester House in California (downstairs where the servants did the dishes - they were washed in the deeper area so as not to break easily and then drained on the shallow end. The sink was also used for laundry!)
I would love one like this in my garden!
Great piece! Love these kinds of finds!