Written by Jack Christensen
Here's a rating system to use when determining the quality of a Curta. It certainly is not cast in stone. Please edit these ratings as needed. Many collectors may think it is far too strict.
The intent of this rating system is primarily to make it less likely that Curta buyers will be disappointed following a purchase transacted over the internet. As a seller, the rating system will help eliminate a disgruntled buyer because of an inadvertently misrepresented Curta.
The rating scale generally deals with appearances only. Thus, an "excellent" appearance Curta might be one that does not even work. Depending on the extent of the internal mechanical problems, a Curta's rating may or may not change. Regardless, the great majority of mechanical problems can be fixed. But see below for a word on repair costs.
This rating system is not meant to directly set Curta prices simply by the relative appearance of the instrument. Many other aspects of a Curta must be considered when determining its value. Of great importance in determining the selling price of a Curta is the age of the instrument. Older Curtas must be given some leniency when evaluating them. A very old Curta in good condition will always draw a greater price than a late production model in mint condition...sometimes by a very significant amount.
A very common problem with grey body Type II's is darkening or "yellowing" of the grey crackle paint. This discoloration can occur even with minor handling and/or exposure to light. Also, the paint on the main body and the collar will often change by differing amounts (probably due to different paint batches used when painting the two parts). The reaction everyone has to this discoloration is purely personal. When the paint has changed "on its own" and overall discoloration is present, the question is raised whether the Curta's rating should be lowered. And what if the body and collar are slightly different in color? Many collectors don't care; some do; many don't see the difference unless two machines are held side by side. Photographs often mask this color change, or accentuate it. Unless the Curta were to be rated "mint" in all other regards, discoloration of the grey paint should probably not be of any concern. A "mint" Curta with discolored grey paint is an "excellent" Curta. An "excellent" Curta with discolored grey paint is still an "excellent" Curta.
Also note that Curtas that have some historically significant provenance will bring higher prices. For instance, a Curta that can be documented as having been used during an Antarctic expedition has more value than a similar appearance unit that was simply stored in a desk drawer for 50 years. A Curta documented as being used by a famous inventor or engineer is a significant collector's item and will command a higher auction price.
And most important is this: The appearance rating given to a Curta can be adjusted depending on the overall impression you get of the unit. A small flaw can always be found on every Curta that is not in "Mint" condition. If the Curta looks "Very Fine" in general, it is just that...don't focus on a very minor flaw to the detriment of the rest of the machine. Curtas that are "Excellent" but for one flaw listed in a category two or more steps lower, can often be rated just one category lower. Again...A rating is determined by the overall impression that the machine gives you (except "Mint" where the machine must really be perfect).
The condition of a Curta's metal or plastic storage cannister also influences the price of the instrument. See below for a comment on the availability of replacement cannisters.
Also note that when a Curta is sold with its original serial numbered cardboard box (older boxes are brown without any printing, newer boxes are sky blue with white printing) the value of the Curta is higher. Older boxes are more valuable. Sometimes an outer cardboard shipping box with the original buyer's address is supplied. Instruction manuals (there are several styles) and warranty cards also add to the price. Original boxes and Curta instruction manuals sold as separate items are valuable, too.
Curta advertising literature, magazine article reprints, original magazine articles, complete magazines which include a Curta article, publisher's tear sheets of such articles, and manual reprints, are also valuable.
Important Information Regarding Curta Repair Parts
Replacement parts needed in repairs can cost between $10 and $600 (w/o installation labor). Even the simplest lever or gear can cost $40. Some Curtas that look nearly perfect on the outside can incur major expenses to replace broken parts inside.
Most broken or damaged Curta parts can be replaced with NOS (New, Old Stock) parts. But some NOS parts are very rare. One such part is the central "tens unit" on a Type II. As of 12/8/04, there is only one NOS "tens unit" known to exist. Of course, such a part could be obtained by disassembling a Type II "parts unit".
Similarly, the metal clearing lever for the Type I is in short supply. Unfortunately, many clearing levers have been damaged when placing the instrument into its cannister. If the clearing lever is not moved to its storage position before replacing the cannister top, the extended ring portion of the clearing lever will catch the edge of the cannister, resulting in a bent or broken part. There are few "uncommitted" NOS metal clearing levers remaining. (That is, clearing levers that have not been put aside for installation on a Curta "just in case".) The remaining metal clearing levers will most likely be installed only on very, very old Type I Curtas. An "everyday" Type I with a broken metal clearing lever can be repaired, but the broken metal clearing lever will be replaced with the more robust style plastic clearing lever used on all later manufactured Curtas.
Another rare item is the bottom foam cushion for a Type II cannister. There are only a few NOS Type II cushions remaining.
There are no NOS metal cannisters for the Type I or Type II. As far as "used" metal cannisters are concerned, there may be a few. But these extra cannisters are often retained as a back-up part by the owner of a Curta (i.e., used cannisters are rarely available as a stand-alone spare part). There are a few NOS plastic cannisters for the Type I, but none for the Type II. If a Curta is purchased without a cannister, it is going to be very difficult and costly to obtain a replacement cannister for that machine.
NOS clearing plates, body shells, and knurled hand grips are also very rare. There is only one NOS Type II grey painted body shell and upper collar available. There are no new bottom nameplates for a Type II.
Curtas in need of parts no longer available are usable only as a "parts unit" for another broken Curta. Such "non-repairable" Curtas can be perfect in every other regard, but be of little value to anyone who wants a complete and functioning machine. Unless you are willing to locate and buy another Curta to disassemble, the value of a Curta in need of an unobtainable NOS part is very low, no matter how perfect it looks in other regards.
Some Curtas in need of many repair parts, even when the parts are available, may nevertheless be useful only as a "parts units". This is simply because the cost to replace many broken parts may exceed the price of a fully functioning unit.