The picture files as a whole are duplicated on this microfilm. They appear to fall into 24 distinct subseries. Most bore letter codes followed by sequential item numbers assigned by the photographic department in which or for which we have assumed the negatives were produced. The letters AMC, C, D, I, M, MC, O, ODH, and PO indicate these subseries. MC stands for McCormick Division or Works, while AMC and M are believed to be its subsets. Other divisional designation include D for the Deering works and line of implements; C= Champion, O= Osborne, ODH= Osborne disk harrows. I refers to IH, an indication of the centralization of the company's promotional programs which occurred around 1915. These numbers have been retained and serve as identification numbers for the microfilmed images.

Internal evidence suggests that there were 10 other series which originally bore no prefix letter, but which appear to have been numbered by the same hand. These were produced for the McCormick Harvesting Machine Company around 1900. Prefix letters for the ten subseries have been assigned by the processing archivist as follows: AA, BB, EE, FF, GG, KK, LL, NN, QQ, SS, TT, UU, VV and WW.

All of the negatives were placed in subseries and item number order prior to microfilming beginning with AA. Two informational targets were used in special circumstances during the filming. “Intentional duplicate exposure” appears when the camera technician decided to make more than one exposure of a single negative. This was done for badly stained, very thin, or very dense negatives, to ensure that information appearing in the original would be preserved. “Defective Original” indicates that the quality of the original negative prevented a good quality 35 mm negative from being made. This target was usually used for negatives that were stained, or had been retouched or treated with an etching compound.

As much as possible, an attempt was made to film the negatives in identification-number order. However, because of technical limitations, this was not always possible. Single images are occasionally shot out of sequence, and sometimes small groups of images were spliced onto the microfilm at the end of the reel. In most cases, the images will only appear one or two frames out of order.

There are two printed indexes to the microfilmed images. One is a subject guide which lists identification numbers according to one of nine broad subject areas: dealerships, employee relations programs, expositions and fairs, farming, places, plants and operations, portraits, product lines, and railroads. A second index serves as a master list of all negative identification numbers and includes such information as date, place, setting, function, activity, product, and image quality. These indexes come from an MS Access database compiled at the Historical Society.

Many of the data elements used to index the images appear in code. Below is a listing of the codes and their definitions.

Date

• Date: appears as Year\Month\Day

• ADM Administration
• ADV Advertising
• ASS Assembly
• DEA Dealerships
• DEL Delivery
• EMR Employee relations
• EXT Extension Division
• FAM Family
• MAI Maintenance
• MFG Manufacturing
• MOP Machine operation
• MPO Machine posed
• P&O Plants and operations
• R&D Research and development
• RAW Raw materials
• RR Railroads

• BYD Barnyard
• DLE Dealership exterior
• DLI Dealership interior
• EXP Expedition
• EXT Exterior
• F Field
• FYD Farmland
• INT Interior
• PLE Plant exterior
• PLI Plant interior
• PYD Plant yard
• RD Road
• RRY Railroad yard
• ST Studio
• STR Street
• YD Yard

• EM Employee
• FG Formal Group
• FI Formal individual
• IG Informal group
• II Informal individual