Defender 53-D

Water 500 ml
Metol 3.0 grams
Sodium Sulfite 45.0 grams
Hydroquinone 12.0 grams
Sodium Carbonate (mono) 79.0 grams
Potassium Bromide 1.9 grams
Water to 1000ml

Developer used at a 1:2 dilution. Development time 45-60 seconds (quite fast for a paper of that era)

I found the formula on an instruction sheet for Du Pont Defender Velour Black projection paper.