Well, while I'm talking about China, here's another postcard from Beijing (formerly known as Peking). This one has a caption so is easily identified: The Observatory, Peking.....it depicts three of the very old astronomical instruments at the Observatory: (left to right) a sextant , a theodolite, and an armillary.

My question this time is: what do the numbers on the cancel represent? I'm guessing the "28" is the year, 1928, but what about the others?Any stamp collectors out there know the answer to that one? ....Here's the cancel, which is rather dark, but appears to be from Peking: