To the left of the stamp are PO boxes and parcel post being transported, to the right of the stamp someone is collecting their old age pension from the post office and a blue post office van setting out on its journey below.
The lower half of the sheet features a globe with South America centre stage and Uruguay marked, below that are all the accoutrements needed for philately. But look at the man posting a letter, here is a little bit of Britain in Uruguay, a Penfold hexagonal Postbox. Designed by the architect John Penfold in the 1860s and (depending on which source read), it was either exported after the 1878 Paris Universal Exposition or the result of an direct export order in 1869. Whichever it was it was an instant success and today there are still six extant in Uruguay, one of which is in Montevideo, but differing from UK ones in that they are painted blue and black.
Lastly on the bottom right is something that spans the eras, that is a hand holding a pen to make a signature as it would have done in 1827 and facing it a hand holding a key which signifies cryptography and the use of digital signatures using special hardware and software, very much the 21st century. There is a more in depth look at this sheet with lots more Uruguayan knowledge than me on DJBM's Philatelic blog
An entry to Viridian Postcard's Sunday Stamps