How come this is a “working” unit?
The seller doesn’t say what “working” in this case means. It could mean that it is “fully working” after you enter the key.
I don’t know this receiver, but it could be that the coordinates displayed could be derived from the C/A code. Military receivers need to be able to receive the C/A code as well, as A stands for “Acquisition” and that is needed to get a lock on the P(Y) code within a reasonable time.
What is special about it? It is very rugged and I believe that this one might be submersible.
I see it is using the Military Grid Referencing System, with 1m precision – and showing its current location as the Rockwell Collins factory in Cedar Rapids, Iowa. 
I presume that is a start-up default, as it looks like the unit has been very recently cold started.
Might be interesting for a collector, but I wouldn’t buy this with the intention of using it.
I think he has misplaced the decimal point – £9.99 seems more like it
Some googling gives this. http://www.fs.fed.us/ne/fia/datacollection/manualver2_0/PLGR_Setup.pdf
So maybe the unit has not had the secret key updated and thus can receive the open GPS signal?
Because of the security module installed in it, the PLGR is a very sensitive security item. As an operator of
these receivers, you are assuming a great responsibility, one far above that of just another expensive piece
of equipment. PLGR “ownership” is transferred to a duty station and the crew leader is primarily
responsible for the daily security of those receivers. The crew leader is required to inform all users of the
receivers of the security and accountability responsibilities. Only USDA Forest Service employees or other
non-federal agencies with a Memorandum of Agreement (MOA) with the USDA Forest Service are
permitted to operate the PLGR. Currently, the Maine Forest Service is the only agency with an MOA with
this Forest Inventory Unit.
Shipping
Your receiver will need to be “rekeyed’ at least once a year as the Department of Defense (DoD) changes
the access code yearly .
Very interesting stuff!
Military receivers need to be able to receive the C/A code as well, as A stands for “Acquisition” and that is needed to get a lock on the P(Y) code within a reasonable time.
I thought the military could jam the A code totally and still get a military GPS to work, but maybe not?
Your receiver will need to be “rekeyed’ at least once a year as the Department of Defense (DoD) changes
the access code yearly .
One would assume that if there were any hostilities, they would change the code immediately, and reissue the new one to those in need. Otherwise there is no point…
The seller says “UK only” so presumably doesn’t want trouble with export regs etc.
I thought it might be handy for when there are jamming exercises But it doesn’t even have a moving map, so the cockpit workload (plotting the coordinates) would be high.
Another one here
The description talks about “highly accurate azimuth and pitch data”.
How do you get that from a GPS?
