Before i deployed to the first gulf war one of my uncles gave me a couple things that belonged to my uncle robert who was killed in VN.

The first is a patch, either squre or diamond shaped, i'm not sure the correct orientation of the patch, its blue thread on white background with a dragons head.  the tongue of the dragon is sticking out its mouth and is trangular or arrowhead shaped. The second iten is a white metal pin with black enamel?  Two crossed arrows and a dagger and saw "de oppresso liber" on the bottom. the back of the pin has is marked D22 which looked like a mold mark or lot control number to me.

Patch sounds like 18th airborne corps

Pin is Special Forces "de oppresso liber" "To liberate the oppressed"

What CQB27 said
XVIII Airborne Corps

SF Crest

Yep, those are them.  Although the patch doesnt have that rocker(?) along the top.

Would a colorfull patch like that have been worn on BDU's or is it something resticted to dress uniforms?

What does "18th airborne corps" mean?  is that like an army regimen/battalion/company or something.  Being a former Marine i have no knowledge of unit patches or Army unit breakdowns.

A Corp is composed of several divisions

Divisions ae composed of several brigades

Brigades are composed of several battalions, then companies, platoons, squads


Colored patches for class A's or dress blues, subdued for BDU's (cammies), only exception is the 1st Infantry Division (Big Red One)

The 18th Airborne Corps is comprised of a bunch of divisions and units such as the 82nd ABN, 101st ABN etc. They're located at Fort Bragg, NC.
http://www.globalsecurity.org/military/agency/army/xviii-corps.htm

The SF crest is worn on the Green Beret as well as their class A's.

Quoted: A Corp is composed of several divisions Divisions ae composed of several brigades Brigades are composed of several battalions, then companies, platoons, squads Colored patches for class A's or dress blues, subdued for BDU's (cammies), only exception is the 1st Infantry Division (Big Red One)

This would depend on what year it was. When we first entered VN the Army was still wearing colored patches and white name strips on their fatiques. During the VN war they switched to subdued patches etc.