the following is said to be the old formula for Perceptol but I have no concrete proof of this.

Sodium Tripolyphosphate 3.5 gms # buffer not required with pure water.
Metol 5.0 gms
Sodium Sulphite anhyd.100.0 gms
Sodium Chloride 30.0 gms
water to 1 Litre

use as stock, 1+1, 1+2 or 1+3.

At 1+2 you would have 600ml of working strength using 1gm of metol.