All the earlier stamps have no serial number. In 1949, China Post printed the serial number on commemorate stamps and special stamps, and the seiral number became one of characteristic of P.R. China stamps. In the past years China has issued more than one thousand stamp sets, but the method of number stamps has been changed many times through time and history.

C-headed Commemorative Stamp and S-headed Special Stamp
The first C-headed stamp set C1 was issued on October 8th, 1949 and the last set C124 was issued on March 10th, 1967. The first S-headed stamp set S1 issued on October 10th, 1951 and the last S75 was issued in May 10th, 1966. The format of C-headed and S-headed stamp serial number is like this, for example, C124 Learn from Heroic No. 32111, the serial number marks as " 124 . 3 - 2", the Chinese word is short for , means Commemorative ( is short for means Special), "124" is the number shows it's the 124th set of C-headed stamp, "3 - 2" means the stamp set total has 3 item, this one is the 2nd. And also you could find "(405)1967" on the right foot of the stamp, it means this stamp was issued in 1967 and it's the 405th item of the whole C-headed stamp. Not all C-headed and S-headed stamps have the mark of the issued year, C16 and before, S5 and before have no year mark.

W-headed Stamp
W-headed stamp total has 19 stamp set, the first set W1, Long Live Invincible Mao Zedong Thought, was issued on April 20th, 1967, the last W19, Revolutionary Youth, was issued on January 21tn, 1970. It's the period of Chinese culture revolution, the numbering of stamp was abolished, so you could find there're no serial number marks on the stamp. Later these 19 stamp sets were number as W-headed stamp.

N-headed Stamp(Stamp with Serial Numbers)
From August 1st, 1970 since January 15th, 1973, China total issued 95 stamps, they were not classed as Commemorative or Special stamps, just numbered with the serial number of issue, so only a number and issued year were printed on the stamps.

J-headed Stamp and T-headed Stamp
J-headed and T-headed stamp was started in 1974, The pinyin J(means commemorative) and T (special) added to the number. Stamp set J1 was issued on May 15th 1974 and J185 the last was issued on November 16 1991. T1 was issued on January 1st 1974 and the last T168 on September 14th 1991.

Stamp Numbered Chronologically
Since 1992, all commemorative and special stamps were numbered cronologically by year and set number, looks like "1992-1(2-1)T", numbers in parenthesis indicates number - position of stamp in set, the letter T/J shows the stamp is special/commemorative.

Regular Stamp
Regular stamp number with letter "R" with the serial number of regular stamp. The first regular set was issued in 1950 and the last was issued on January 1st 2004, and the issue was continued since 1950, but no serial number was printed on regular issue.

Airmail Stamp
The airmail stamp issued only for airmal and numbered with "A" and the serial numner. China total issued two airmail stamp sets, A1, issue date 1st May 1951, A2, issue date September 10th 1957.