Written by GoldSmithWatchWorks Sunday, 09 May 2010 07:09

Crystals:

the sapphire crystal is modern invention. this watch is from 1950,,, 60 years ago,

a- sapphire is scratch resistant and a high  clarity type crystal. the downside is that it fractures very easily--- and scratches cannot be "buffed" out 

b) mineral glass scratches much easier than sapphire, and in most cases cannot be buffed out, but it is stronger and has higher resistance to breakage...

c) plastic/acrylic crystals are the best overall, they work in dive watches, including the bulova 333 and 666 feet versions, they resist breakage due to their ability to absorb shock.. in addition, scratches are a breeze to buff out and can be buffed many tines

d) hardlex and other coated mineral glass crystals are better then straight mineral glass but scratches  cannot be buffed/polished out economically vs getting new crystal,

e) straight glass crystals from 1940's are regular sand glass, must be thick to resist breakage

f) celluloid crystals are those from 1900 to 1940 that become yellow to brown over time, similar material to old 16mm film. can be buffed but this material reacts to many chemicals and gasses. alcohol will melt it.

thus for 75% of vintage watches have plastic and 25% glass.

one would be smart and wise to continue to use plastic crystals as original to vintage watches.

they are inexpensive to replace, very strong, impact resistant, they can be buffed AND the crystal, in 90% of cases forms the seal to the case! plastic/acrylic crystals are machined to fit cases with various channels and other edge type grooving. many SNAP IN forming a secure pressure seal. some have inner steel rings to provide dual pressure system.




Crowns:

Most vintage watches have signed crowns, but not all models have signed crowns. It depends on year produced and where the case was made.  

ie: bulova cases were made in France, W. Germany, Germany, Switzerland , usa, ..

In many cases a particular model may have been made in several different countries depending on model and/or year,

When you combine the fact that crowns are a weak point in a watch, stems break, rust out etc. and then replacements are used, and then many years go by, proof that a signed crown may or may not have been correct to a particular model can only be determined by comparison to an exact similar model. 


As far as this particular Oris, it is THE EARLIEST DATE HAND CALENDAR MODEL ever made by Oris. 

Most versions offered have 17 jewels vs the the 7 jewel  of the  model we are offering.

Thus, this model is the first one, it has 7 jewels that protect the most friction prone portion of the movement: the escapement

http://goldsmithwatchworks.com/faq/27-new-to-collecting/378-dsfas4.html

7 jewels actually mean that the movement has a jeweled escapement – two hole jewels and two cap jewels (one each for each end of the balance wheel shaft), two pallet jewels and a roller jewel.

Most common movements of this period were no jewel or one jewel on the bottom of balance shaft. The 7 jewel movement was introduced as a means of preventing wear caused by the high speed of the escapement. This setup was common in older pocket watches and pocket watch movements used for wrist watches of the same period.



rock
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