Pro. Image has a pgi of 43 compared to 44 for gold 200. So slightly finer grain. Gold 100 was pgi 42. All for 6x4
It is as i understand it an overcoated version of gold 200 making it more neutral and which also made it economical to produce.
The 100 is an e.i. Not iso, which tells you all you need to know about its origins.
Shooting gold 200 @100 vs pro image @100 would be a closer comparison.