Sheldon lathe model numbers and serial numbers generally consisted of two series of number and letter designators. The serial number was stamped on the tailstock end of the bed and the model designator and serial number were stamped on the gearbox plate. The last two digits of the serial number were stamped on the machined area for the witness mark on the base and also the top of the tailstock when there were several lathes of the same size being made (to avoid tailstock mix-up). These numbers and codes provide identifying information for the machines. For example, the number stamped on the gearbox plate of a particular lathe produced in 1973 reads "ES-46-P" and the number stamped on the tailstock end of
the bed is "ES-32633." Together, these numbers identify this lathe as a late model 11" swing lathe with 46" bed (20" between centers) and an "E" type drive (coincidentally, with 8 speeds), mounted to a pedestal type base. Sheldon used a fairly consistent nomenclature system, with some variation. They
began the combined model/production order system in approximately 1940. Previous to that, there was less consistency.
Model Identification (Tag on Gearbox) generally included:
1. The Swing and Type of Drive with one or two letters, e.g., SE,
2. Then the Bed Length in Inches, e.g., 56,
3. And how the lathe was Mounted, i.e., P for Pedestal or B for Bench, e.g., SE56P or sometimes ES56P.
Size/Capacity (Model) Designators
L 10" swing #4MT spindle taper; 1-3/4" x 8 T.P.I spindle thread
XL 10" swing, "short" #5MT spindle taper; 2-1/4" x 8 T.P.I spindle thread
K Early 11" swing, "short" #5MT spindle taper; 2-1/4" x 8 T.P.I spindle thread
S Later 11" swing (clearance measures at an actual 11-1/4" over the bed and
carriage wings), "short" #5MT spindle taper; 2-1/4" x 8 T.P.I spindle thread
M 12/13" swing, "short" #5MT spindle taper; 2-1/4" x 8 T.P.I spindle thread
(This lathe was designed to swing 13" but was advertised as having a 12"
swing)
R The most modern, sophisticated, and heavy duty lathes of the Sheldon line. The R series includes 13", 15", and 17" swing lathes
Drive Type Designators
E 4 -speed under drive with 4 step pulleys (or possibly 8 speeds if the primary
pulley has two steps instead of 1). A very reliable drive.
U 4-speed under drive using 2 levers & dog clutches
Q Quick-change feedbox, generally used with a W indicating something non-
standard at that time, usually a feed clutch in the apron
W Was also used later to indicate the Worthington variable speed spindle drive
Spindles
The smaller Sheldons (L, XL, K, S, and M series) were available with three types of
spindles - threaded, L-00, and D1 (camlock). Threaded spindles were the standard and were the most common. Spindle styles were not part of the model/serial number system and were only mentioned on the shop order when the lathe was being built. On the larger (R-series) lathes the D1 spindle became the standard, with the L or the A spindle nose as options.
For your information, the large 32" swing Sheldon CNC lathe, built to be shown at the 1982 IMTS but which never left the plant, had a D1-8 spindle as standard equipment. It had a 30 HP variable speed DC spindle drive and was scheduled to go to Texas right after the show but National Acme changed all that!

Common Bed Length Designators
L and XL Series (10") came in 38", 46", and 56" lengths
K and S Series (11") came in 46", 56", and 70" (special order) lengths
M Series (12/13") came in 46", 56", and 70: lengths
R Series (13", 15", and 17") lathes came in 5 ft., 6 ft., and 8 ft. bed lengths. The 8 ft.
bed had a third support pedestal in the center.
Less Frequently Used Letter Designators (Usually on older model Sheldon
lathes)
R Sometimes used for rear drive on a bench lathe. Also sometimes used to indicate tapered roller spindle bearings
T Indicated a taper attachment or tapered roller spindle bearings
M Sometimes used at the end of a serial number on Government orders to
indicate the order included a metric end-gear attachment.
O & H Both used to indicate a flat belt overhead spindle drive
B Occasionally used to indicate ball bearing spindle bearings (very few were
made)
The Numerical Portion of the Sheldon Lathe "Serial Number" (Order of
Production, Stamped on the tailstock end of the lathe)
The "serial number" is stamped in the tailstock end of the bed, sometimes preceded by the model number, e.g., "ES-32633." This is a system of sequential serial numbers, in order of machine production, started before 1940 and continuing through all the Sheldon lathes, including the NC and CNC lathes. NC and CNC were numerical controlled lathes. The system was continued to the end of Sheldon production. The database of these serial numbers is only approximate as the original production records are no longer available. I am attempting to reconstruct the database, so if you have known production data on your lathe (the preferred document is the signed and dated test sheet that accompanied the lathe; second in preference is an original bill of sale; etc.), please contact me so I can include this information in my database reconstruction project and fill in the gaps.
Here is a list of what I have thus far.
Serial Number Production Date
549 1939
LP-1524 August 27, 1940
LWQU-5838 1943
LS-6182 1944
ESWQ-11388 October, 1945
SWQE-12014 1946
XL-56-TX-16934 1952
TMU-19208-T 1953
TSE-19925-1 1954
XL-22222 December 14, 1955
EM-23928 November 10, 1956
EXL-27182 February 17, 1960
1710-NC- 31899 September 20, 1969
1710-NC-32010 January, 1971
1710-NC-32117 May, 1971
1710-NC-32157 February, 1972
1710-NC-32366 November, 1972
R15 -32621 November, 1973
ES46P-ES-32633 November, 1973
1710 NC-32634 November, 1973
1710-NC-32705 June, 1974
1710-NC -32799 January, 1975
1710-NC-32926 July, 1975
1710-NC-33090 June, 1976
1710-CNC-33152 January, 1977
1710-CNC-33197 October, 1977
R15-33272 April, 1978
R17-33337 Marcy, 1979
R17-33412 February, 1980
1710H-CNC-33476 May, 1980
1710H-CNC-33490 April, 1981
R15-33511 August, 1982
The first Sheldon lathes were produced in 1932 or 1933 with these, I believe, having "Sheldon" cast into the beds. The oldest "model/serial number" The oldest surviving example that I know of is L-172, this being discovered in 2024 in an email sent to tony@lathes.co.uk. The lathe and its serial number are shown below; it was probably built in 1933, five years before R.S. Dean sold the Sheldon line to the Armstrong brothers and George Caroline in 1938. The sequential serial numbering system was used until production ended. The oldest verified, recorded, dated serial number produced by the Sheldon factory is 549, dated 1939 while the youngest I know of is #33511 produced in 1982 - this being one of the last of around 33,500 manufactured..