John Deere Model '630' Series
The 630's were introduced by John Deere in August of 1958 for the 1959 model year.  This is why many think that they were 1958 tractors.  They were built in three configurations - Row Crop, Standard and Hi-Crop.  The Row Crop version is the most common.
The 630 is the last two cylinder in the John Deere line that started in 1934 with the Model "A".  The "A" became styled in 1938, was upgraded in 1944 and again in 1947.  In 1952 the Model 60 appeared and in 1957 the Model 620 was introduced.  The 630 was an upgrade to the 620.  There were no major mechanical changes made to the 630 except for the cosmetic changes to the sheet metal and operator's station that were designed by Henry Dreyfuss and Associates.
Since 1920, all farm tractors have been tested at the Tractor Testing Laboratory at the University of Nebraska in Lincoln, Nebraska.  However, none of the 630 tractors were tested there since there were no changes to the engine, transmission, or rear ends of these models.  The Nebraska tests for the 620 models apply.  Test number 598 covers the 620 gasoline powered tractors and test number 604 covers the All-Fuel model.
The John Deere specifications are:

    Gasoline powered    44.16 drawbar HP    48.68 belt HP
    All-Fuel powered      32.66 drawbar HP    35.68 belt HP
    LP-Gas powered      45.78 drawbar HP    45.78 belt HP
Model 630 Production

Serial Number breaks are as follows:

    1959    6300000 to 6312040
    1960    6312041 to 6318206

Total Production by Year

    Model                                  1959      1960         Total

    Row Crop Gasoline           10397      4857        15254
    Row Crop All-Fuel                 120          61            181
    Row Crop LP-Gas               1249        623          1872

    Standard Gasoline                474         231           705
    Standard All-Fuel                      5             9             14
    Standard LP-Gas                    14             2             16

    Hi-Crop Gasoline                      3             7             10
    Hi-Crop All-Fuel                        2             1               3
    Hi-Crop LP-Gas                        3             0               3

    Total Production All Models                             18058