Brownells sells both manganese and zinc sourced from the Parker company itself, so it is original. In its plain state, the manganese is charcoal gray and the zinc is light gray.
From: MIL-DTL-16232G
1.2 Classification. Coatings are of the following types and classes, as specified (see 6.2):
Type M Manganese Phosphate Base
Class 1 Supplementary preservative treatment or coating, as specified
Class 2 Supplementary treatment with lubricating oil conforming to MIL-PRF-16173, Grade 3 or MIL-PRF-3150
Class 3 No supplementary treatment
Class 4 Chemically converted (may be dyed to color as specified)
With no supplementary coating or coating as specified
Type Z Zinc phosphate base
Class 1 Supplementary preservative treatment or coating, as specified
Class 2 Supplementary treatment with preservative conforming to MIL-PRF-16173, Grade 3 or MIL-PRF-3150
Class 3 No supplementary treatment
Class 4 Chemically converted (may be dyed to color as specified)
With no supplementary coating or coating as specified
3.2.5 Chromic acid rinse. (Classes 1, 2 and 3). The chromic acid rinse of classes 1, 2, and 3 shall be performed in accordance with the following:
a. The final rinse shall be hot 63 to 93oC (150 to 200oF) chromic acid or chromic phosphoric acid solution: approximately 300 grams chromic acid flake in 1000 liters (L) of water.
b. The final rinse shall be maintained at a pH of 2 to 4 by the addition of flake chromic acid or mixtures of chromic and phosphoric acids. The pH of the final rinse shall be checked at least every 8 hours.
c. The final rinse shall be checked by a standard free and total acid titration or pH reading as often as is necessary to assure that the bath remains within the limits set at all times during which it is in operation.
d. All rinses should be discarded whenever they become contaminated. The final rinse shall be checked at least every 8 hours and shall be discarded when the total acid reading rises to more than 7 times the free acid reading.
e. The item should remain in each rinse for a minimum of 60 seconds.
f. Following the chromic acid rinse, the item shall be thoroughly dried before application of a supplementary treatment, as applicable.
3.3 Stress Relief. Unless otherwise specified (see 6.2), parts with a surface or throughhardness of Rockwell C 39 or greater shall be given a stress relief treatment. This includes carburized, induction hardened, flame hardened, etc. treatments. Also, any part that is ground, cold formed, cold straightened, etc., that may induce residual tensile stresses after machining or heat treatment shall be given a stress relief treatment. The stress relief treatment shall consist of a heat treatment at 177 to 204°C (350 to 400°F) for a minimum of one hour for every inch of thickness but not less than one half hour for thicknesses less than one-half inch. Optional heat treatment for carburized parts is 104 to 155oC (225 to 275o F) for 8 hours.
3.4 Hydrogen embrittlment relief heat treatment.
3.4.1 After coating. Unless otherwise specified (see 6.2), parts (including carburized parts) having the hardness values shown in Table I shall be given a hydrogen embrittlement relief heat treatment after coating per Table I without any parts developing cracks.
3.4.2 After baking. Unless otherwise specified (see 6.2), all lots of parts or materials for which baking is required shall be tested for hydrogen embrittlement.