The estimated production curves for the YORK Band Instruments are based on instruments for which serial number and date of manufacture are known. In addition, an estimation of monthly output in the early part of the century and a correlation of serial numbers with patent dates which appear on certain York instruments has been taken into account. Six individual yearly production rates are plotted above, and it is projected that the closest estimate of the actual year of manufacture can be estimated by establishing a range of possible dates from these production curves. For example, an instrument with the serial number 28000 could have been made between the years 1904 and 1910, depending on the actual rate of production. It is believed that the yearly production rate of 2750 instruments comes the closest to meeting all the criteria used to establish this table, but variations in yearly production are not known, so the range of dates is probably the safest way to "guesstimate" the date of manufacture.