** The actual dates of manufacture of engines before 1913 have yet to be discovered. The numbers shown are based on the dates of the sale of the engine/automobile. From the available data it appears that engines were installed in cars, or sold as engines only, in numerical order until summer of 1912. In late 1912, however, engines were assembled and numbered, and then stored for later installation. Consequently serial numbers and dates are no longer in order.

In the summer and early fall of 1912 engines were made in a separate plant (only known as "Detroit" in the records, and these engines were given "B" numbers 1 through 12,247. These B-series engines were installed in random order beginning in October and ending in December 1912. To add to the confusion, there is a gap in the regular serial number sequence of 12,247 numbers, somewhere between 157,425 and 170,000. We have found no evidence of engine numbers in the 158,000 to 169,000 range. During these three months, a mixture of the B-numbers and the regular numbers were used and by the end of December all the B-numbers were used.

It appears that the engines of this period were warehoused and removed at random, sort of a last in, first out sequence. For example, B-numbers in the B-1,000 to B8,000 range were used in October, B-7 to B-12,000 in November, and B-5,000 to B-12,000 in December.

Ford's records show 157,425 as the first number of fiscal 1913 (October 1, 1912), yet cars with engines in the 153,000 to 157,000 range were sold in October (in addition to the "B" engines). 169,### to 173,### in November, and 169,### to 183,563 in December.