Apple on its website sellsLG’s UltraFine 4Kand5K displaysas recommended options for its pro customers, but soon the company may start selling an unreleased LG model as well.
This was discovered byPierre Dandumontin macOS Mojave 10.14.4 beta 2 whichreleasedfor testing on Monday, as highlighted today by the French blogMacGeneration(Google Translate).

The assets in question include a new hardware identifier denoting the unreleased monitor—0x5b74 instead of the current 0x5b11—along with a macOS icon representing the device..
The icon is literally the same as that for the current UltraFine 5K, suggesting there will be no major design changes. The slight bump in model identifier indicates this could very well be a revision to the existing UltraFine display rather than a brand new model from LG.

The curious icon is most likely just a placeholder that will get replaced with an up-to-date device image when the macOS Mojave 10.14.4 software update is released publicly in a few weeks (after all, the monitor is pictured with the outdated Mac OS X Tiger wallpaper).
LG released its 4K and 5K monitors at the end of 2016, following the first MacBook Pro model with Thunderbolt 3. The iPhone maker collaborated with LG on these monitors to ensure they meet the needs of its pro customers (at least until newApple-branded external displays arrive).
LG has since released multiple external displays based on the speedy Thunderbolt 3 protocol, including a34-inch UltraWide 5K displayfeaturing a wide 21:9 aspect ratio.
What do you make of this discovery, boys and girls?