The title mentions hercules. It has a 9pin connector with a few pins missing.

it's likely to be an MDA monitor.

weedeewee wrote on 2025-07-17, 17:28:

The title mentions hercules. It has a 9pin connector with a few pins missing.

it's likely to be an MDA monitor.

I asked about it because the seller sells it on multiple sites with different pictures and I can't find any info on the picture tube. It's an Orion R12CP39-DH.
The seller also hid the fact that the was retrobrighted at some point, here is the original condition.

I tried searching for the "MMY 89101" on the deflection coils and rather surprisingly the only result points to some Korean website about a Sanyo 15kHz composite monitor!

Based only on this point it might be CGA (but the pinout suggests against this theory) or MDA (the latter is 18 kHz but at least according to my Fenice composite monitor it's relatively simple to convert a 15 design to a 18, and the pinout more closely matches that even though I haven't spent much effort to figure out if it's for the plug or the socket)...

However the Sanyo monitor's yoke is actually different in what could be the second line of the model number...

I can see the reasoning behind your guess too - the individual controls and the shell are clones of the IBM 8503, which along with the 8513 were the first VGA monitors 😮

That is a monochromatic CRT. Considering the missing pins in the plug it would be MDA or mono CGA monitor.

Deunan wrote on 2025-07-21, 18:02:

That is a monochromatic CRT. Considering the missing pins in the plug it would be MDA or mono CGA monitor.

It's very likely MDA/Hercules. The three missing pins are R,G,B, but the MDA "Video" pin is present. A monochrome CGA monitor usually has just "V" missing, and uses a resistor-based "DAC" to generate ~16 shades of green/amber/gray from the CGA color bits.

Bit the bullet and bought it, it's actually a super long persistence green monochrome. Love it!
Thanks for the help, guys.