These ‘Goliath’ calendar pocket watches (known as quantième lune) were very popular (and in mass production) from about 1890, made by various manufacturers. I know nothing about Longines – but they were also made by Louis Brandt: before the beginning of the Omega ‘operation’ but nonetheless Omega. The (27’’’ 30-hour) movements of the (Louis Brandt/Omega) version were the same as the pocket watch of the same size (with the added calendar complication). And they continued to be produced after the start of the Omega operation in 1894 (and therefore appear in the Omega Archive). The calendar watch gradually dropped out but production of the 27’’’ 30-hour (in quite large numbers) continued until at least 1905, parallel with the 27’’’ 8-day (for which there was no calendar version).
These watches are cool, and huge. Did people carry them, or were they meant to be desk / travel clocks?
Again I can only talk about the Omega versions – but I guess it reads across. Omega produced two sizes of ‘Goliaths’: the 27’’’ (with a case diameter of just under 70mm) and the 30’’’ (case diameter 75mm). As you say, big for a pocket. It gets more complicated. The early 27’’’ 30-hour had a smaller movement, approx. 45mm (about 20’’’) (which was also used in other smaller 30-hour pockets) – just as we see here with this Longines. The later 27’’’ 8-day (and the 30’’’ 8-day) had much larger movements (approx. 61 and 67mm respectively). But those same 8-day movements were also cased in two much larger cases (40’’’ and 60’’’) – and those were definitely for display stands (and were typically sold with the stands, either leather-covered or silver-fronted stands). So now we come back to the ‘standard’ Goliath – and hence your question. At roughly 70mm I guess those were too large for most pockets. Many were definitely sold with display stands (like the two larger versions) and many stands still exist. The catalogues from the period show an option of buying the watch with or without the stand. The following shows what I have tried to describe. The smallest is a 30’’’ (the others are 30/40’’’ and 30/60’’). The OP’s watch would be slightly smaller but would probably have been displayed in a similar stand.