KWANGSI: Republic, AE 10 cents, year 10 (1921), KM-Pn3, L&M-168a, pattern in copper, PCGS graded Specimen-50. E. Kann wrote his book he states that these were possibly struck at the mint in Philadelphia. This was based on the fact that the patterns often show up in the USA, as well as a collection Kann viewed when witting his book. The owner of that collection was of the view that these were struck in Philadelphia. Basically the Philadelphia mint theory is just conjecture and not based on any solid fact. It is also possible that they were struck at Kwangtung. The Kwangtung mint at this time was one of the largest mints in the world (previously set up by the British). Kwangtung is also very closely located to Kwangsi and seems most logical.
Estimate: 400-500 USD