R. C. Allen entered the typewriter business in 1950, with its complete buyout of the Woodstock Typewriter Company, of Woodstock, Illinois.  R. C. Allen had previously manufactured both adding machines and cash registers, as well as precision instruments for aircraft (such as altimiters.)  Allen, through its purchase of Woodstock, attempted to compete directly with such other firms as L. C. Smith & Corona, and Remington-Rand, who were offering full lines of office machines.  Production of the typewriters initially continued with little change, and although some alterations were made over time, none appears to have been significant.  R. C. Allen finally ended typewriter production in 1967, having produced, it is thought, about a million typewriters.
R.C. Allen 6

Jim Dax collection

Jim's machine is a very early one, for R.C. Allen production; it is serial number 1,100,468, which by the existing records indicates that it was only the 468th unit produced under the new ownership.  It does display some stylistic changes as compared to the final Woodstock machines, one being the pushed-out sides at the rear.

At least one very early R.C. Allen machine has been spotted which has a front label plate giving the R.C. Allen name in large letters, with 'Woodstock' spelled out below this in much smaller letters.  Thus, it appears that at the very beginning, the machine was to be called the R.C. Allen Woostock Typewriter.  Obviously, this did not last very long, since by the time Jim's machine was built, this practice had ended.
The first R.C. Allen machines, like that seen above, are referred to as Model 6.  This is because, even though an incredible number of mechanical alterations had been made to the machine, Woodstock never broke out its serial numbers from the "Model 5" block from that machine's inception (in 1917) until the buyout.  The machines simply stopped displaying the "No. 5" and were simply, after a time, referred to only as the "Woodstock."  This is why the first R.C. Allen machines begin at Model 6.
R.C. Allen 700

Tilman Elster collection

Within a few years, R.C. Allen changed the model number to 600 and then quickly to 700.  This machine is a Model 700, with serial number 7-1865032 which correlates to 1955. 

There has been some debate about the application of the brand, or model name "VisOMatic."  This machine has this label, on the front, right side.  Otherwise, though, it is very similar to the earlier Model 6 and 600.
R.C. Allen 700

Will Davis collection

This machine is serial number 7-1870583E, built 1956.  Note the label of "VisOMatic" applied to the front.  This machine incorporates margin set buttons on the carriage, which function similarly to those originally offered by Royal as "Magic Margin."
R.C. Allen VisOMatic "A"

Tilman Elster collection

This machine is referred to in the official serial number list as the VisOMatic A.  It should be noted that following the 600 and 700 models, a Model 800 appeared in 1957, and that this machine's serial number, which is 8-2165235-15, includes a prefix of "8."  The "-15" seems to indicate platen width.  This example dates to 1960.

It may prove out that machines with this appearance should actually be considered Model 800, and that those which appear like the second Musicwriter seen below are actually the VisOMatic A.  At present, the whole existing serial listing for Woodstock and R.C. Allen machines is, in fact, in question.
MUSICWRITER

Tilman Elster collection

The patented "Musicwriter" music typewriter was based on the R.C. Allen standard.  This machine is serial number 8-2165060-16, indicating construction in 1960.  It is based on the Model 800 / VisOMatic A.  Note that the music-writing machines do not have carriage return levers, tabulators or ribbon selectors.
MUSICWRITER

Tilman Elster collection

This later Musicwriter is serial number BC-2340105-16.  It is based on the VisOMatic A by serial number, but we can see that there have been some changes in decor.

Again, it may prove that machines with this appearance are actually the VisOMatic A, and that those with "older" appearance as the previous two machines are really Model 800. 
R. C. Allen Woodstock 6

Will Davis collection

This is a curious example which displays a dual branding.  The front label clearly includes both the new R.C. Allen name and the old Woodstock name, and seems to indicate that, at least for a brief period, the new owner was feeling the effect of losing the recognition of the original brand name.  This example is serial number 6-1111349 12, manufactured in 1950 and with 12" platen.  Note the use of separated windows in the paper table, as on older Woodstock machines -- probably due to the wider carriage on this model.
R.C. Allen Vis-O-Matic B

Ned Brooks collection

This machine is an extremely late example.  It has serial number B2454497 and was made in 1967, which was the last year of production.  At present, it is the highest serial number known to the author.  It also types in an unusual 8-character-per-inch all-capital font.