Where can I find information on the original STANLEY Sweetheart logo?

Prior to 1920 The STANLEY Works and STANLEY Rule and Level Co. existed as two separate companies. The STANLEY Works had been using the heart logo with SW inside it for some time before the merger in recognition of William H. Hart, who served the firm for 61 years and was Chairman of the Board from 1915-18 (he “retired” at age 84 and died the following year).
To properly commemorate and symbolize the merger, the company invited employees to submit ideas for a new logo. By popular decision, the “Sweetheart” trademark, what we now call the Sweetheart logo on STANLEY tools was born. It was combined with the Rule & Level’s notched rectangle.
Although the use of the SW in the heart was formally dropped in favor of the simple notched rectangle in 1934, the older combination logo still came out of the plant on various products lines until the old stock was used up over the next several years.