The package contained, in Stewart’s words:
Some kind of whatsit, and a very advanced one at that.
The prop used is a piece of electronic circuitry showing an American voltage and frequency of 110-volt 60-cycles. If you look closely at the first image you can see S.G.E. marked on the circuit board.
The first image was taken during the examination by Stewart and Elín following their brief rest at Dreki in the Highlands. (Episode 1 – The Messenger Boy).
The second image was taken during the meeting with Commander Nordlinger at Keflavík US Naval Air Base. (Episode 3 – The Deception Operation).
The prop appears to be in better condition in the second shot, having lost a pin in the first shot. This would indicate that the scene shot in Commander Nordlinger’s office was shot first. This is quite possible as the Nordlinger scene, purportedly at Keflavík US Naval Air Base, was most likely filmed in the UK prior to the production crew travelling to Iceland.
The filming location of Nordlinger´s office is, at the present time, unknown. Due to the location of the production (BBC Scotland) it is possibly located in the Glasgow area of the UK. More images of the filming location can be seen here.
Enquiries still continue with staff at S.G.E. Analytical Science Products (Trajan Scientific and Medical) in order to identify the circuit board. It was thought that it might be the circuit board from a syringe cleaner made for S.G.E. by Royal Electronics, however it appears now not to be the case. 
If you can help identify this circuit board please make contact.
Images © BBC Scotland.
1. Addinall, A. (2014) pers. comm 25th November, 2014