Manufacture	Rado
Model	Diastar
Reference	623.0001.3
Movement	Quartz/ETA 2783, 25 jewels at +3 spd
Serial No.	XXXXXX
Case	Tungsten Carbide, 36x45x13mm
Crystal	Sapphire facetted
Dial	Black/Champagne Sunburst
Bracelet	Original NSA, 16,5cm around
Lugs	18mm
Production	1973
Condition	Excellent
Service	Not necessary
Box	Yes
Papers	No

This Rado runs at +3 seconds per day! Still the unbeatable chronometer... For sale here is the Chronometer only. However, the quartz with black dial can be purchased as a package deal, in fact together with the Rado Balboa? Each watch has a separate box.. All three for 1295 euro.

This is the uncommon chronometer version of Rado's original Diastar design, costing a princely sum of 2300 euro or 2600 USD at the time (130.000 yen, as is consistent with advertising of the period). Made in the early 1970s, it is very much like the 1962 Diastar which also featured a segmented, applied hour chapter, date window at 3:00, and the 'original' oval Diastar scratchproof case. Of course, featured prominently is the Rado anchor which moves when the watch moves; this is not always the case, Rado even used mineral dials, marble or quartzite. This can usually be deduced from the fact that the printed or applied anchor logo is used instead of the moving anchor, which is characteristic for Rados with automatic movement. Only automatic Rados with mineral/gem dials featured printed anchor logos, but not as a cheap option, but as possibly the only way to keep the fragile dials intact through production.
The 21600, 6bps ETA 2783 movement (rebranded Rado 2797) with incabloc, date quickset, center seconds and 46h power reserve, has a Triovis micrometer-regulation and the COSC-registration number engraved. It also has had a necessary superior internal refinishing to achieve chronometer status. The COSC was founded 1971 as a non-profit-organisation to standardise the Chronometer norms of the Swiss observatories, so this DS 1E is made around 1972 - 1975. It is very rarely seen as every single movement was certified with a test log, making it so very expensive.
This larger model however, measuring 35x45x13mm, has a facetted sapphire crystal, very uncommon at the time and therefore of course advertised as such. The case front shows no wear, as it is Tungsten Carbide (therefore it sold originally with an unconditional warranty of three years). The condition is 'Very Good' to 'Excellent' and the ETA 2783 movement is keeping accurate time; service history is unknown, but the movement is clean; date functions properly at midnight.
The original NSA bracelet with signed Rado clasp is present on this watch. Original inner and outer boxes are present as well. A lot of Rados in the late 1960s, 1970s came on NSA bracelets with Rado-signed clasps. The Novavit SA (NSA) was sited in Carouge, Kanton/federal state Genf/Geneve, Switzerland and was liquidated in 1999.
It had been founded in 1947, the business was to produce bracelets for the watch industry with almost blanked parts and also blanked parts for the whole fine mechanic. It seems to have been the family enterprise of a family called Nobs. The company logo is a triangle inner a circle.NSA became world famous for their very comfortable high quality watch bracelets, especially for the so called 7-row. This was applied for patent in 1966 and patented in 1967. Probably they also had a patent for their clasps - both, the short and the long (folded) type have a spring mechanic which makes it automatically a bit longer if there´s enough pressure, e.g. in the summerheat, when the wrist swells a bit.
I´ve seen 7-rows and 3-rows with signed clasps of a lot of watch companies in Switzerland as Tag Heuer, Jaeger LeCoultre, Rado, Felca/Titoni, Zodiac, Technos, Roamer, Louis Rossel, ... .
They also had been available in the aftermarket with NSA-signed clasps.
7-rows had been also produced in USA (Kreisler, under license) and Italy (I don´t know if licensed or for NSA).
You can find NSAs in a lot of variations in material (SS, GP, titanium, "bicolour", synthetic material, PVD-coated) and surface design. The company still registered a few patents in the 1980s but finished work in 1995 (finally liquidated 1999).