Stadia Match Output

Number:94a

Maker: Unknown Chinese
PHOTO

Length: 25 cm

Gauge Marks: ρ"

Scales Front: SC&T T T = C A SC C2 = D ρS ρS

Scales Back: S1 2 3 4 = D 1 2 3 4 = S1 2 3 4

Info: FanHsiu Chang Collection
The following is from FanHsiu
SC should be sin*cos, T be tan, C2 be cos^2.
SC&T is for θ smaller than 35'
since θ is small, sinθ*cosθ = 1/2 sin2θ = θ = tanθ
Two ρS scales are new to me, check 90 on ρS scale is around 2.06...
I guess S is sine, that ρ is likely 180*60*60/π ~ 2.063
If so, ρS scales is for θ from 35' to 90°, ρS would be from ~0.021 to 2.063
The black number and red numbers on the same ρS scale should be 10 times different.
For example, ρ90° is ~2.063; ρ6° is ~ 0.2156
But I don't know how ρS is used in surveyor's calculation.
One the back, S1234 on the top stator is ST scale divided into 4 segments.
S1234 on the bottom stator is S scale divided into 4 segments.
Quite an interesting rule, though no maker name or model number on it.
It is even in an apparently wrong Tianjin 6504 box.
I am guessing it was made by Shanghai.