Ah yes - there are no signs because it is still national speed limit in all directions - no signage is required, as there is no change. Rumble strips may cause a driver to reduce speed, but "maxspeed" is for the legal limit of the road, not the driveable limit. So on the A4 dual carriageway (and on A5 DC link to the old Ballygawley roudabout) I have marked as
maxspeed=70 mph
maxspeed:type=GB:nsl_dual
[NB: This is the established norm for UK national speed limits: the maxspeed:type contains the signed NSL and type of applicable road; maxspeed contains the highest legal speed by any vehicle (in this case, car/motorbike/light van) and is provided for routers which don't yet process the UK NSL tags. Once they do, they should show the lowest of the two tags, dependent on vehicle type.]
Similarly, on the single carriageway A5/A4 I have set as
maxspeed=60 mph
maxspeed:type=GB:nsl_single.

The nearest national speed limit signs are on the Grange Road approach from Ballygawley (signed 30 mph) to the old roundabout.