Silva Prospector

This compass was purchased in December 2003 on eBay. It is essentially a RECTA compass, made in Switzerland, for the Silva company. These can be purchased today under the RECTA brand name, although the case is now made of Noryl (plastic).

 I received this compass on 5 Jan 2004. I originally thought that the mirror was designed to be used by looking down through the face of the compass. However, when I received it, it was immediately apparent that this is incorrect. This is a sighting compass, an object is sighted along the long groove on top of the compass, and the bearing is read via the mirror on the bottom.

According to the patent, the mirror is designed to drop down beneath the compass face as the unit is opened, and to come to rest at a convenient angle, so that the user, while sighting along the groove in the top of the case, can easily read the bearing.

Specifications:

• Manufacturer: RECTA (Labeled for Silva)
• Date of Manufacture: Post 1956 based on patent
• Materials:
• Body: Aluminum
• Crystal: Plastic
• Capsule: Plastic with knurled aluminum ring.
• Size: 2 5/8 X 1 13/16 closed, 4 1/2 X 1 13/16 open
• Needle: Magnetic steel
• Damping: Liquid
• Pivot: Jewelled (?)
• Graduations: Degrees by 20, with tick marks at every 2 degrees.
• Declination: Adjustable via screw-driven gear.
• Weight: 3.6 oz
• Stop: None.
• Damage: The most obvious damage is the presence of a 1/4 inch diameter bubble within the capsule. This bubble has the potential to interfere with the operation of the compass. There is a mark within the plastic capsule, which could indicate the presence of a small crack in the capsule. Various dings and nicks on the exterior, and the lanyard is frayed near the attachment point to the compass.
• Other: Luminous marks on the North arm of the needle both top and bottom, a pair of luminous boxing lines at the North mark on the dial, a set of four luminous dots, one each at 290, 315, 45 and 70 degrees. These appear to be phosphor as they 'charge' and become more luminous by exposing to a bright light. Luminous alignment mark at the lanyard end, proceeding from the lanyard opening to the sighting notch, another alignment mark in line with the sighting notch on the lanyard side of the capsule. A luminous mark in line within the sighting notch, at the opposite end of the case from the lanyard. This last 3/8 inch of the sighting notch is pitched upward to facilitate viewing when sighting an object through the sighting notch.

Also noteworthy is the fact that this needle appears to be balanced for high latitudes. Where I am (N 35) the southern arm of the needle nearly drags the bottom of the capsule. Further north (N 45 or farther) it probably behaves better.

  RADIOACTVITY WARNING

This compass contains radioactive elements.  I measured a 5 minute average of 1500 CPM in the area of the luminous mark on the end opposite the lanyard, and about 600 CPM in the area of the luminous marks where the lanyard attaches to the base. At 12” the activity had fallen off to the level of the background (25 CPM).