The CRT319H was probably not from Olivetti, but AT&T purchased it outside Olivetti. The H, to me, seems like an HITACHI design. It should be written inside somewhere. This CRT319H monitor is able to display the same standard resolution of an original AT&T/OlivettiM24/VDC board, but also displays correctly the EGA resolutions, and supports TTL interface with 3 video signals (RGB) and 3 intensified signals (RI GI and BI), so it has a total of 6 video bits, for a maximum of 64 colors displayed concurrently). The CRT318T (or CRT318H, because it seems this exists also this version) only displays correctly the original Olivetti resolutions (up to 640x400 16 colors, while using and EGC2413 display enhancement board). But the EGA resolutions are stretched and with not a good aspect ratio. And this doesn't support the 64 EGA colors as defined by the standard. I also have 3 VDC750 boards so I was able to see the result on the CRT318T. I don't have a CRT319H. If you have an Olivetti color monitor you can check the manufacturer by looking below the tiltable round base of the monitor itself. There is printed in blue ink somewhere a T for Toshiba or an M for Mitsubishi. The CRT 313/H is a Hantarex monitor, but it is not the Hantarex 1231. The CRT 314 is a monochrome monitor that is larger than the CRT 313, but still has the proprietary connector and works fine with a 6300.