What markings to look for on original brake booster?
 

I am not 100% sure my brake booster is the original so how do I tell if it is?

Can you post some pics?

Any codes or pad printed markings on the surface?

K

The markings/stampings will be on the back of the clamshell. Look at the small square tabs. If looking at the front it depends. Is yours painted or bare? Normally old leaks and such cause pitting under the master cylinder area of the booster and somewhat to the left and right bottom area. That's an indicator of age and likely originality. If yours has the Delco Moraine stamp the stamp difference is the aftermarket letters are all there and have thin lines. The letter O is a closed circle while an original "O" looks like 2 U's on top of eachother. Originals they stamped sloppily. Most times they are missing a letter at an end of a word or the stamp is deeper on one end and a soft strike on the other end. The original letter stamping is also fatter. It would really help you if you went to a car show and compared some to your own cause then you can spot them a mile away. Otherwise post a pic as Keith said and most can tell you right away.

The other difference is the triangular dimples. Originals will have softer smoother points while aftermarket are sharper and more angular. They are punched deep and steep on the edges.

I am going to try posting a picture and hope it works. I hope it helps me size it correctly.

The finish appears correct. Pontiac used a flatter/Duller Zinc Dichromate finish.
The triangular dimples look like the smoother original kind I mentioned earlier. The O in Moraine is the correct split look BUT looks like someone tinkered with the Delco Moraine stamp to make look it more defined.

I'll focus on the E in morainE as it's easily the most suspect. It's a little off axis from the rest of the word. It's sharp and clear and looks thinner than the R in MoRaine. Originally it would have all been struck with the same force and pressure as the rest of the word and the N is a weak hit right next to the hard defined E. A single letter would not have been hit harder like that originally. At the factory sometimes the stamp wobbled left, right, up or down as it struck that is why you see things like your M barely showing but the O and R are more distinct. The letters should show a consistant level of force or trailing force left, right ,up, down applied across all your letters. Your's don't. The L and C may also have been "clarified" by someone too but I would say it's an original booster that someone down the line tweaked.

Is this finish close to the way it was when new? Its kinda dull now and if that's the way its supposed to be I will leave it alone but I was wondering if i could do something to brighten it up. Could I use a semi gloss clear coat or is there something I should try.

Clearcoat booster a bad idea?
 

I posted a picture of part of my booster and realize its supposed to be kinda dull but I do not have a new original that has the correct finish to look at, I would like to know if they can be clear-coated to improve the look without making it look worse. I am not doing a restoration but have cleaned and repainted most of the engine compartment.

X2 on thinking yours is an original booster. Usually spraying with a clear, even a satin clear will produce a shine. Try going to car shows and look for original/survivor cars and look at their booster's, take pics and compare. Maybe someone here will post pics of theirs. The booster on my 72 Formula is dull like yours, but like you I'm not sure if it's due to age, even though my car only has 58K miles. One things for sure, don't get into a Hurry to do something you might later want to undo.