Honestly, I would have guessed RBA but since P-E said he never seen metal plates in RBA vests.

Like you suggested, it might could be aluminum oxide. If it is indeed "AO" then it's earliest RBA plates.

The RBA plates have a special form. The back plate is lightly courbed.

Here's picture of both plates ;

Front :





Back :




As you can see, it's write "DO NOT DROP" on my plates. But it isn't write on all RBA plates. So this words aren't a reference for us to ID your plates.

This model of front plate was already worn during Somalia war, in 1993. It was this model with "cut angle". Why cut ? Because it's better to use weapons. And as you can see, each model of current SAPI plates have this cut angle.

The back plate have a special slice form. It's not completly flat, there's a small slope. I'll try to find you a picture (I sold my plates, so I can't take a picture of it, but I know someone that have them).

Hum, at this time no. Problem is that there's some and some different body armor and plates. Metal was used as ballistic material, but was then replaced by ceramic (in Vietnam war, the pilot and aircrew already had ceramic/glass fiber plates in their Chicken Plates body armor) because this one offer best protection and less risk of hurt : ceramic fractures and retains bullets / metal bend and deforms, so there's some additionnal risks to hurt the body.

I'm not sure...to be honest I've no idea. But it's not exclude it's for the RBA, but in this case it's an earlier model that only serves for experimentation or training. In combat situation, they only used ceramic plates. I'm almost sure of that.

But I'll do some research for your plates and I'll tell you.

Well, I just find an old picture of a back plate for the RBA, with that, you can see the slope I try to explain ;



this is the real back plate for the RBA, the one in ceramic. You can see the form of this plate. Is your like this ?

Is it possible that these were handmade by an individual? I know that sounds kinda silly, but these are unlike anything Ive personally seen.

P-E wrote:The RBA plates have a special form. The back plate is lightly courbed.

Here's picture of both plates ;

Front :





Back :




As you can see, it's write "DO NOT DROP" on my plates. But it isn't write on all RBA plates. So this words aren't a reference for us to ID your plates.

This model of front plate was already worn during Somalia war, in 1993. It was this model with "cut angle". Why cut ? Because it's better to use weapons. And as you can see, each model of current SAPI plates have this cut angle.

The back plate have a special slice form. It's not completly flat, there's a small slope. I'll try to find you a picture (I sold my plates, so I can't take a picture of it, but I know someone that have them).

These are for the RBA ranger Body Armor, I use to have these for my early RBA very cool
paul

I have an idea...it can be for a coutermine set (light set) called Body Armor Set, Individual Countermine (BASIC).

Here's the description of someone on USMF : "Ballistic Body Armor 10 Piece set. Several sets available. Consist of the following: Helmet Cover, 1/4" Face Shield Riot, Ballistic Colar, Vest with metal chest plate, Upper Right & Left Arm. Lower Right & Left Arm, Antifragramination Trousers, Groin Pouch with Metal Plate".

Here's picture of the set ;









In fact, there's not some metal plates used currently, so the number of body armor that contains that sort of metal plates is realy reduced. Well, it's an hypothesis...but it can be it...