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Presented is an absolutely outstanding and near flawless “Collector Quality” example of this maker’s sextant which was made for the U.S. instrument firm, Weems & Plath, and bears their Serial No. 61689. It comes with the original Mahogany wood case with upgraded 4 x 40 and 6 x 30 scopes and a special astigmatizer filter which is designed to be used with a whole horizon mirror. As of 2008, the 6 x 30 scope is no longer available from C+P which makes this a scarce and valuable combination. The handle, index arm and telescope are exactly the same as would have been found on a Carl Plath sextant of the same period. Replacement cost today is over $1900.00 with a single telescope which makes the value of this two scope package package about $2250.00

PROVENANCE: This sextant has sat on a closet shelf in an Idaho home for the last fourteen years. It was owned by a U.S. Navy navigator as personal gear, and used in frequently as a back-up while he was in the submarine service. When purchased by the last owner, there was no certificate. That is of no importance, since C&P contemporary sextants were made to a standard instrument error of less than 10 arc seconds which for practical purposes may be considered without error. Cassens and Plath is not currently related to C. Plath, but in the past, Theodore Plath, Carl’s son was a partner. It is the only German manufacturer still producing sextants. Read its history below. This two scope sextant is in such excellent condition that it can be considered, “as new”. It is ideally suited for someone seeking a quality German brand for use at sea or as part of a collection.

CONDITION: There is little discernible evidence of wear or use so that it can be considered as new in all respects. It operates like a well oiled piece of machinery, and has one minor fault. Both mirrors show as NEW. The only issue is that the lighting wire has separated from the terminal and needs to be soldered in place. The bronze arc has only the slightest patina of age. Index error is 2 minutes on the arc, and there is negligible side error.

This is the one of the finest examples of a previously owned Cassens & Plath sextant imaginable and is suitable for a collector or for use at sea . It requires someone who can appreciate the fine points of a sextant, and is willing to pay an appropriate price for this level of quality and excellence.

STAR RATING: This fine Collector Quality instrument rates
FIVE STARS irrespective of age.
QUALIFICATIONS: We are one of the few company’s still selling navigation instruments that know anything about them. For purposes of judging whether Joel’s opinion counts, he was the editor
of the chapter on sextants of the 1977 Edition of “Bowditch”, The American Practical Navigator, NAVPUB 9; a member of the
U.S. Naval Academy Navigation Symposium Board, 1975 -1978; the author of a book on marine sextants, Cornell Maritime Press,1975,
and the founding president of Nautech Maritime Corporation which partnered with Tamaya of Japan in the introduction of the
MS 733 Spica, the MS 833, Jupiter, MS 933 Venus sextants and the famous NC-2 navigation computer, in the U.S. market. Joel is a retired Master Mariner, and held a U.S. Navy “D” Qualification as a Senior Skipper – Oceans. For
six years he was a Varsity Offshore Coach at the U.S. Naval Academy.

Some of his memberships include the: Association of Naval Aviation, Silver Wings,
The Tailhook Association, Naval Academy Sailing Squadron, McCampbell’s Aces Squadron, Naval Historical Foundation, and
the Naval Order of the United States.

COMPANY HISTORY: At the turn of the
twentieth century Hamburg, on the river Elbe, the home of C. Plath (named after founder Carl Plath) was the leading seafaring port in Germany. However it was being challenged by Bremen, that other great North Sea port on the river Weser.
Plath was at that time the unchallenged leader in the manufacture of nautical instruments
on the European continent. However it had always had a difficult relationship with the Bremen shipping companies and shipyards. The firm realized that if it wanted to do business in Bremen, German parochialism demanded that it have an office in that city. In 1908 Theodore Plath was offered a partnership in Cassens and Benecke when one of the original founders of the Bremen company – Benecke – suddenly departed. At that stage the company founded by Tanne Janssen Cassens was only 6 years old and was a minnow compared to the whale that was C Plath. It is my understanding that the company was not even an instrument manufacturer but rather a trading company servicing the port of Bremerhaven. Theodore Plath only accepted on condition that the partnership’s name be changed to Cassens and Plath. The C + P partnership never had any intention of manufacturing sextants and other
nautical instruments. It was simply a vehicle for the marketing of C. Plath compasses, sextants and nautical instruments into the Bremen trade. It also acted as a chandlery and repair service for Bremen ships carrying Plath instruments.
This arrangement worked until 1962 when C Plath sold out of the partnership
and the two companies went their separate ways. It was from this point onwards that C + P began to manufacture their own instruments, no doubt heavily reliant on C Plath designs. Therefore, there are no Cassens & Plath sextants older than 1962.


Measuring Range: -5 to 125 degrees
Telescope: 4 x 40 Coated optics
Frame: Bronze with black
enamel paint and bronze arc.
Micrometer Drum and Vernier Scale: reads to 10 seconds of arc
Index Mirror: 56
x 42 mm. aluminized on the rear side.
Horizon Mirror: 57mm diameter.
4 for index mirror
3 for horizon

Weight sextant: 4.2 lbs, Weight case 6 lbs.


1 Cassens & Plath (Weems & Plath)
Sextant frame
1 4 x 40 Scope
1 6 x 30 Scope
1 Special astigmatizer lens
1 Mirror adjustment tool combined with screw driver
1 Brush
1 Varnished Mahogany sextant case with key

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Shipping & Packaging

The cost of shipping, packing, handling, and insurance to your destination, will be calculated point to point and is an additional charge. You may email us to get these costs. We price our shipping honestly, but we expect to be reimbursed for the nominal cost of packaging materials and handling.

Our Unconditional 'No Nonsense' Guarantee

If not completely satisfied with your purchase it may be returned, if without damage, within three days of receipt in its original packaging. Return items must be insured for their full value. Only a prior email authorization by us for the return is required. Shipping charges are refundable if due to our error within the continental United States.

International buyers welcome, but inquire first. We have satisfied customers worldwide.

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Established in 2003

Celebrating 18 Years of Exellence in Nautical Antiques

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