We've been enjoying these strikingly beautiful views of London by night, produced as promotional material by paint manufacturers Pinchin, Johnson & Co. Ltd. The closest we've got to a date is 193?, and Worldcat throws up a number of similar materials from the 20s and 30s exploring the subject of London (and more broadly, English domestic) architecture. They're very much aimed at architects and other people in charge of making buildings happen, with a strong emphasis on durability, quality and expertise. But their marketing copy is the least of it – it's the images themselves that make the case.
They are printed using offset lithography, but where modern printers would use solid spot colour or composites derived from four standard colours (CMYK), our Pinchin Johnson printer has mixed his own colours (blues, yellows and blacks). We suspect the pigments – whether from expense, toxicity, or difficulty of use – would be very difficult to reproduce in the modern era. Perhaps even the technique itself is nowadays accessible only to fine art printers. You'd be unlikely to get something of this quality through the letterbox if Google advertisers got the idea that you were redecorating.
I'm afraid we rather fell upon these as things that would make lovely gifts (including to ourselves), but there are a handful left if you wanted to drop by and look at them.