T'ien Ch'i T'ung Pao

Description	Obverse	Reverse	Diam., mm	Peculiarity	Image origin
The Ming Dynasty Emperor Hsi Tsung (a.d.1621-1628) c.d. 1621-28			26	S1209 ch.kung on rev. (Board of Works)	B
			26		A
			26	S1207 ch.hu on rev. (Board of Revenue)	A
			24	S1202 look at the comment below the table	B
			25.3		A 03-Jan-98

Please look at T'ien Chi script variations.

There are some additional considerations about 4-th coin (signed as S1202).
Coins with the same legend were casted during rebel state Tien Wan Kuo (1352-1358) by the Pretender Ch'en Liang of Han. In that case it's S1117-1118 coin.
Prices on Rebel T'ien Ch'i coins are much more ( >100 times ) then on Ming coins.
Differences between Ming and Tien Wan Kuo coins were described for me by Mr.Gilbert Tan:

The most glaring difference is that on the Ming version the character Chi, which is the bottom character, has a horizontal line protruding out of the left radical. The Yuan Rebel's version does not have this protrusion.
The metal for the Yuan Pretender's coin is less brassy (more greyish-white). The Ming version is significantly more yellow in shade, and that kind of metal was only used after 1400 AD, with the exception of the value two Mongol script coin bearing Zhih Yuan as the year-title.