This vintage Johnson Bros. blue Willow pattern shallow bowl/ saucer (made in England), was likely made after 1912 (based on the back mark, source.)
Related: #AskTamara: What do you use to test for Lead?
As with nearly all of the Willow pattern china I have tested, it was positive for very high (unsafe) levels of lead when tested with an XRF instrument. In general I would recommend not using these dishes for food use purposes, ever. [More info about the concerns here.]
If you have more information (or links) about dating the piece (based on the back mark) please let me know!
The test results for this particular dish:
- Lead (Pb): 43,100 +/- 1,700 ppm
- Mercury (Hg): Negative (ND/ non-detect)
- Arsenic (As): Negative (ND/ non-detect)
- Cadmium (Cd): Negative (ND/ non-detect)
- Tin (Sn): 99 +/- 24 ppm
- Barium (Ba): 424 +/- 93 ppm
As always, please let me know if you have any questions!