Compass with adjustable declination

BPL sells such compasses—check the site.

I don't think the BPL compasses have an adjustable declination. Although there are probably lighter I have the Suunto M-2D Locator Compass that does have an adjustable declination (1.3 oz).

http://www.rei.com/product/408011

Also, an old trick, particularly if much of one's trips are in geographic proximity—tape on a declination arrow to the bottom transparent side of the
compass capsule at the relevant angle. Not elegant but fully functional. Not so good for a 2000 mile thru-packing trip.

BPL sold the Brunton Baseplate Map Compass 7DNL which had a declination scale—but is out of stock. .91 oz.

For anyone researching this topic on BPL..
Declination is the angle between magnetic North, and the true North pole, as measured from your location. It varies by region. Maps indicate true North, and of course a compass measures magnetic north, so the declination angle (called variation) must be added or subtracted when converting a bearing from a map to a compass.

A compass with adjustible declination allows the user to set the local declination once, by rotating the boxed orienting arrow independently of the azimuth (numerical) ring, so that arrow would no longer points at N. From then, the user boxes the magnetic needle in the orienting arrow, and then reads TRUE North off the compass azimuth ring. This is easily transfered back and forth to a map where the lines are also true North.

For example, in your area the variation might be 10'E. Rotate the non magnetic arrow 10' to the E, and always box the magnetic needle inside it. A mountain you see in a direct line with "S" on your azimuth ring is at a bearing of 180 TRUE on your printed map.

Some GPS with an internal compass allow the user to specify the local variation, then display true bearings.

Some compass watches such as the Casio Pathfinder allow the user to 'tell' the watch where North is. If you calibrate the watch pointing at true North, all subsequent readings will be true.

The lightest compass I know of with adjustible declination is the 1.1 oz, $12, Brunton 9020G.
http://www.brunton.com/product.php?id=116

The lightest compass I know of with tool-adjusted declination was already mentioned, the Suunto M-2 series.
Note: Suunto's own website says it does not have adjustible decliination; it is wrong.
"Fixed declination correction scale"
http://www.suunto.com/suunto/main/article_1column.jsp?CONTENT%3C%3Ecnt_id=10134198673939521&FOLDER%3C%3Efolder_id=9852723697223448&PRODUCT%3C%3Eprd_id=845524442490150&ASSORTMENT%3C%3East_id=1408474395903523&bmUID=1176865870732&bmLocale=en_US

My compass weighs 1.20 oz w/ its lanyard. It has a mirror and declination markings. I've never really needed to do much navigation with it, but the declination where I hike is only about a half of a degree. I don't think my compass is quite that precise anyway.
Its a cheapy Silva that I picked up at either MC Sports or an Army Surplus 4 or so years ago. Its kind of like this one:
http://www.silva.se/templates/Products____81.aspx?epslanguage=EN&productId={895110A6-8F06-4E77-A6AB-77FBED440102}

Adam