Lee's Amortizer
The Lee's Amortizer Alamo Model slide rule was manufactured in the United States in the late 1940's. Patented by Smith Lee in 1947, this 14 inches by 2.5 inches wood fabricated rule was designed to calculate the amount of the monthly payments of a loan for a given annual interest and the number of months-years to pay the loan. It seems that in 1947 Smith Lee also patented another similar rule for banking use, the Profitizer. The Lee's Amortizer is finely varnished and its 20 scales are painted on the wood. The scales are labeled accordingly to the value they represent.
On the front face of the Alamo Model rule are the scales: Monthly Payment (upper), ranging from 5 to 100, and Amount to be Paid (lower), ranging from $1,000 to $20,000. On every side of the slider are nine scales for specific annual interest rates: 2%, 2.25%, 2.5%, 2.75% 3%, 3.25%, 3.5%, 3.75, and 4% on one side, 4.25%, 4.5%, 4.75%, 5%, 5.5% 6%, 6.5%, 6.6% and 7% on the other side. The divisions of these scales are the number of years and months to amortize the loan, ranging from 1 to 25 years on all the scales, except in the 4% scales that ranges 1 to 40 years.
I don't know if there was a user manual for this rule, but the examples of how to use the rule to solve different amortizations problems are printed in the interior of the packing box.
Next is a document I wrote explaining how to use the Lee's Amortizer Rule and some brief explanation of the Math formulas used
The Lee Amortizer.pdfNext are the instructions to operate the Lee's Amortizer Rule, coming in the interior of the rule box. It seems that there was no other instruction document. With easy examples is illustrated the operation of the rule
LEE'S AMORTIZER INSTRUCTIONS.pdfClick on the next links to other panoramic pictures of other Lee's Amortizer rules
The Lee's Amortizer Alamo Model was not the only amortizer rule created by Smith Lee. There was a previous version apparently patented 1936 and manufactured in 1940, with some important differences with the Alamo Model. The Amount to be Paid scale ranges only up to $10,000, the Monthly Payment scale up to $ 80, and the Annual Interest Rate scales are only divided in moths and ranges from 12-240, it seems that these scales were only 4%, 4.5%, 5%, 5.5%, 6%, 6.3%, and 6.5%. No others are shown in the pics I found in the WEB.
https://osgalleries.org/collectors/wyman/singleline.cgi?string=336
https://www.worthpoint.com/worthopedia/vintage-lees-amortizer-wood-slide-1881708394
Here is a link to the historic file of sold Lee's Slide Rules on E-Bay (Entry Dec-20-2019 corresponds to the purchase of the rule showed in this page):