Rebuilt, refurbished, remanufactured and resold.  Reworked typewriters!
For those familiar with antique typewriters, the machine at left may look somewhat, but not totally, familiar.  It may also surprise you to find out that this Woodstock standard typewriter has a serial number of RN15206.  This would seem to make it a very early Woodstock No. 5, which of course it is.  Or rather, was.  This machine has undergone a complete factory refurbishing, and in addition has been upgraded.
Removal of the added-on front panel reveals a look more normal for a Woodstock.  The machine, when rebuilt, was not only totally "gone over" and tuned up, but also had the front, sides and back enclosed with specially designed panels.  These panels, including the front one, have application of sound deadening material.  The machine was rebuilt by Woostock itself between 1947 and 1950.
You'll note that the paper table doesn't look like that which you'd normally see.  It's much shorter, and has a window running its full width through which you can see the position of the margin sets.  The original plastic window, slightly shrunken due to age and deterioration, is nevertheless intact and still installed.
Here's a machine you've likely seen before at times on my sites.  It's my refurbished Underwood 5, manufactured in 1922.  The machine was refinished in all-over gray crinkle paint.  Machines quite like this -- in other words, refurbished but not upgraded (like the Woodstock seen above) were sold through Montgomery Ward's catalog.  I own a 1961 catalog which, although offering newer machines than this one, shows a very similar decor, including the simple replacement red decals on the paper tables of various makes.

This would be the second tier of rebuilt machines -- you could call them "rebuilt in kind, refinished" as opposed to "rebuilt / upgraded" as the Woodstock above.

Collectors may encounter these kinds of machines from time to time, and most often pass them up.  However, large numbers of machines either upgraded or just rebuilt served in very many offices for very many years, and are a notable, if not valuable, part of typewriter and office history.
At right, the "new, deluxe 1948 model" Woodstock typewriter.  This machine was built at exactly the time that the early No. 5 seen above was REBUILT, and carries some of the same identifying features.

Note the style of the "Woodstock" logo on the front, along with the black crinkle paint.  Most importantly, note the short paper table, with plastic window running all the way across, in which is visible a scale and the margin sets.  Note also the paper edge marker on the paper table.  Yep, same paper table all right, and proof of the date of remanufacture of the old machine above.  In 1950, Woodstock Typewriter Company was bought out by R. C. Allen, so this is the last Woodstock labeled variant.

Note: the No. 5 does, in fact, have labeled on its rear "Made in USA  Woodstock Typewriter Company."
Above, a scan from a 1961 Montgomery Ward catalog showing various Smith-Corona (models 7-A and 88), Underwood (model SX-100 and model 150) and Remington (Noiseless and Super-Riter) machines offered, rebuilt and direct by mail.  On the right, the Underwood SX-100 in larger size.  The catalog states that all machines were factory disassembled, scientifically cleaned, had all worn parts replaced, were fitted with new-style comfort plastic keytops, were given new baked enamel "crackle" finish in either gray or tan, and that all were rebuilt, reassembled, tested and inspected by skilled, factory-trained mechanics.  The prices were well under those for new machines.  Note the similarity of the logo on the SX-100 here and that on my No. 5 seen earlier.
WHO ACTUALLY WAS PERFORMING THE REBUILDING OF THESE MACHINES?  Well, as we have already seen, Woodstock Typewriter Company was rebuilding its own machines, and was not alone among major typewriter manufacturers that did so.  L. C. Smith & Corona Typewriters Inc. also rebuilt its own machines, as did Royal Typewriter Company -- but Royal used the name REGAL REBUILT on those machines on a decal on the rear.  Most interesting is the discovery that, as early as 1911, the Union Typewriter Company had arranged for one of its component companies to rebuild not just its own make, but ANY make of machine.  The American Writing Machine Company ceased production of its last New Century Caligraph machines around 1906, and thereafter performed only rebuilding of machines until the transfer of the manufacture of the Remington Junior to that facility around 1919 (wherein it was redesigned and then marketed as the CENTURY 10, and a product of the American Writing Machine Co.)  So, you see, the major manufacturers DID get into rebuilding in a big way in order to defend against outside firms that were competing for sales.
1911 advertisement from American Writing Machine Company for typewriters of all makes and styles, factory rebuilt.  Describes the company as "the oldest and largest rebuilt typewriter concern in the world."  Note the American Writing Machine Co. emblem on the left.  Note also the address, 345 Broadway, N.Y. which was right by the Remington and Monarch headquarters.  Proof positive that Union Typewriter was into rebuilding not just its own, but any, machines by this time.  (Ad in Davis Family Collection.)
We also know that REMINGTON-RAND was rebuilding Noiseless-design machines itself, both at the original Noiseless factory in Middletown, CT and later at its own plant; such machines are labeled on the rear. 

There were quite a number of independent companies rebuilding large numbers of typewriters as well.  Several of them were located in Chicago; one of the Chicago-based businessmen involved in this business, one
Harry A. Smith, is quite well known to us today.
Here's another machine in our collection.  It is indeed tan in color, and has a crinkle finish; the only word on the machine is the decal SMITH on the front.  It has replacement green rubber keytop covers.

This is a rebuilt LC Smith No. 8, and was one of the later versions of that model with fully enclosed sides and back.  In all likelihood this is a dealer-rebuilt machine.  Normally, when machines were rebuilt by large concerns in blocks of large numbers they received at least something like the original brand name as a replacement decal -- see the gray-colored Underwood and all the advertised Montgomery-Ward rebuilds above.  In this case, an L.C. Smith machine has been rebuilt fully and repainted (naturally) but received only the name SMITH on its front.  You might consider this the bottom rung of rebuilding in terms of relation to original factory manufacture.  You would find, back then, dealers who produced excellent rebuilds -- and ones that weren't so good, either.
To sum this all up, then, we can think of a number of tiers or levels of rebuilding:

1.  Machine rebuilt by original manufacturer and upgraded with newer features.
2.  Machine rebuilt by original manufacturer.
3.  Machine rebuilt by large concern with factory and distribution network or sales agents.
4.  Machine rebuilt at dealer level in own store or workshop.

During the days when typewriters were in production, you might find a dealer in any town that was an agent and even an official repair center for an original manufacturer.  However, there were also repairmen that were not; they simply built their businesses on repairing typewriters from offices in towns and cities.  SOME of them WERE agents for rebuilding concerns, though, like Harry A. Smith or Dearborn Typewriter Exchange and could offer blocks of machines rebuilt by those factories to office managers.  One wouldn't imagine you'd find a dealer representing both a new-equipment maker and a rebuilder though; that would have been a conflict of interest.  As we see above though the manufacturers did take steps to offer rebuilt machines under their own roofs.

The only one of these available to us today is "4," and you can get VERY good work at this level even today.  However, the others are just as gone as the typewriter manufacturers themselves (and the dodo.)  But, for many years, all of these played an integral part in the whole office machine story and should not be as neglected as they are in modern accounts!