A HA

It's a Civilian Labor Group uniform

From the wiki:

Civilian Labor Group or CLG are organisations of German or other European nationals employed by the US Army in Europe. They often wear American fatigues or a blue uniform with various insignia identifying them as CLG members. The Labor Service Units were created during to support Berlin Airlift of 1948-1949. With the creation of the Bundeswehr in 1955, the Labor Service Units were renamed Civilian Labor Groups.[1] The units performed a variety of functions such as Signals, Construction, Bridging, and Security. One CLG was assigned to the US Army's 565th Engineer Battalion.[2]

And coincidentally enough their rank badges are horizontal stripes

Still don't know anything about the stuff on his collar.

EDIT: In German but mainly captions to pictures of badges/pins, etc Link

As far as I can see, the patch doesn't match any from the United States divisions. Looking through some other division insignias the closest thing I have found is one of the tank brigades from the British Army but I don't think it is correct. It is certainly not coming up with any matched on preliminary searches, so it looks like I may need to dig deep. Any idea what it says on his arm band?

I'll keep updating if I find anything else that is relevant.

Edit: Looks somewhat similar to the top row, second from the left in this image but of a different colour.

Edit 2: After thoroughly scouring the main badges of the American forces during WW2 I'm almost 100% sure it isn't one of them which strikes me as odd seeing as his uniform matches other representations of the American uniform. At a guess this would make me think the badge was more honorary, or and award of sorts rather than a symbol of rank within the United States Military. You can have a look through them yourself if you want. http://www.skylighters.org/special/insignia/

Edit 3 - 7 was unnecessary sidetracking.

Edit 8: Patch seems to say something close to EGCO(N)ST. Nothing coming up on several variations of the letters. Highly doubt he was part of any navy seeing as only high ranking officers seem to have their photos taken like that, and even still they have distinctive features (the traditional white sailors cap). The traditional sailor portrait from WW2 would be more likely to look like this. None of these WW2 naval soldiers have any rank on their shoulders.

Edit 9: /u/Gewehr98 was correct, the flat stripes are an indicator of overseas service, after a fair bit of digging I found an image. That at the very least confirms your grand father did fight overseas. INterestingly though, it seems that the US only issued the overseas bar to US soldiers. Will investigate.

OP, would you feel comfortable with sharing grandpa's name? Might help us narrow some stuff down.

The stripes look like overseas service stripes, though I could be mistaken. Three stripes = 18 months overseas.

Still digging on the patch and lapel devices.

Hey everyone, i'm sorry that I went to sleep and couldn't respond straight away. Thank-you for all the help. I've been looking up in immigration everything from 1948-1960 and nobody by my grandfather's name he came up on any documents. I've found some documents written to a nunnery in Geneva and a few people in Šiauliai country expressing how he's sorry for leaving and he would return as soon as possible. The name he left Europe with was Jonas Gatavicius for those asking.

Shot in the dark, maybe the devices on the collar are from the 1st Polish Parachute Brigade?

dimensions of the device are 18 x 29mm

Again, total shot in the dark