There is already a large and well-researched database of typewriter serial number data online at but we have some further data, more specific to US-made standard typewriters and would like to provide this data here.  This is OFFICIAL MANUFACTURER SUPPLIED DATA, and is from (obsolete) manufacturers' materials.  For most uses we recommend Dirk Schumann's site already linked above.
Standard Typewriter Serial Number Lists
Figure 1:  Royal Typewriter Company "Line Book" - Approximate Ages of Office Typewriters by Serial Number.
Notes on Figure 1.  "M" means million; read 2178M as "2,178,000."  As in most lists the actual model of the typewriters is not given - the original purpose of the list was to give a rough guide for age in order that a dealer might better gauge a trade-in value against a new machine.
Figure 2.  Olivetti-Underwood age guide, first page.
Figure 3.  Olivetti-Underwood age guide, second page.
Notes on Figures 2 and 3.  Underwood models are given at the top of the colums; in the case of the No. 3, the carriage widths are included also at the top.  Monarch typewriter listing is for all name and brand variants for the Monarch-style machine; while there are nuances, the machine essentially switched from Monarch branding to Smith Premier branding in 1923.  Remington Standard machine listing through 1929 indicates serial number prefixes.  Remington Noiseless listings are preceded by model number when that model begins.  Remington and Royal serial numbers were not available to Olivetti-Underwood for this publication for 1959 and 1960.  Woodstock pre-1921 not listed.
Figure 4.  Olivetti-Underwood age guide, third page.
Figure 5.  Olivetti-Underwood age guide, fourth page.
Notes on Figures 4 and 5.  Models for L.C. Smith / Smith-Corona in main production sequence not identified except introduction of No. 8 in about 1915.  Meaning of double asterisks at 1953 entry not explained.  Everest - Models S, ST, ST-92 delineated as shown.  Olympia - Model SG appearing in 1953, through 3000.  R.C. Allen is former Woodstock machine; models 600 and 700 delineated as shown.
Underwood rebuild manual
We have in our collection a rebuild manual that covers Underwood standard machines of several models.  This is not a factory manual; it has no publishing information.  This seems to be one of those manuals you would send away for, after having seen a small ad saying "make money in your spare time - learn to repair typewriters!"  The manual is generally thorough, even if not highly polished in text and form but it does appear that the author used official Underwood-supplied data and drawings and may in fact have been an Underwood dealer. 

In this manual is included a table which is intended to help make the ordering of parts easier - but in fact it gives us a breakout of mechanical changes during production of the Underwood machines.  It's known that such machines as the No. 5 continued in production for many years but that it had some changes; this list is the first we've seen that breaks out given blocks of serial numbers as being common.

The PREFIX letters refer to a common general group of parts and are used for internal (company or repairman) identification only.  The regular model numbers as used for advertising, sales and identification are clearly delineated as such.  We have altered the representation of the data to make it easier to understand.
H series (oldest.)

No. 3 (18, 20, 26 inch)     18,500 to 93,000
No. 3 (12, 14, 16 inch)     45,500 to 400,000
No. 5 (10 inch)               517,000 to 1,610,000

K series

No. 3 (18, 20, 26 inch)        93,000 to 100,000
No. 3 (12, 14, 16 inch)       400,000 to 455,000
No. 5 (10 inch)                1,610,000 to 1,750,000

K2 series

No. 3 (18, 20, 26 inch)        100,000 to 4,000,000
No. 3 (12, 14, 16 inch)        455,000 to 4,000,000
No. 3 (11 inch)                   630,000 to 4,000,000
No. 5 (10 inch)                1,750,000 to 4,000,000

A series:  Model 6, all carriage widths     4,000,000 to 4,300,000
B series:  Model Standard, all widths       4,300,000 and up
C series:  Model Master 11, 12, 14 inch   4,755,000 and up
1936 Underwood Standard; DB Davis collection
Keep in mind when using these listings that they're approximate; they also can contradict each other at times.   Age of a typewriter is really less important than the model number or name and the model can be ascertained with certainty while the age is rarely more specific than a whole year in range.
L.C. Smith & Corona Typewriter Co. "Smith-Corona" Model 1-A Standard.  DB Davis collection.