not be able to update the original post any more, but there is a new metering valve:
Brooks instrument NRS series metering valve
unfamiliar to the hobbyists but it is a big name in flow control devices.
Brooks instrument Extremely low flow NRS needle control valve
, Model 8503, 8504, 8513, 8514.
This metering valve is the same design(non rising stem) as Parker Hannifin HR series, and same as Parker HR series, low CV for extremely low flow control.
8503, angle pattern, normal handle
8504, straight(inline) pattern, normal handle
8513, angle pattern, digital handle
8514, straight(inline) pattern, digital handle
stem type Cv.
type 6, CV: 0.052
type 5, CV: 0.017
type 4, CV: 0.0057
type 3, CV: 0.0013
type 2, CV: 0.00066
type 1, CV: 0.00029
in picture is the type 1, highest precision model, with lower CV than a Parker Hannifin H0 model(the best of Parker).
sorry about the distortion, they r cell phone pictures.