There is a recipe online that it comprised of: bergamot oil, lemon oil, sandalwood oil, neroli oil, grains of camphor, rose water and cologne spirits (whatever that was). But it certainly sounds like it would have a lovely aroma.
A terrific website with many photos and history of Hoyt, go to www.cliffhoyt.com:
"In the early 1900's, E.W. Hoyt and Company introduced two new sizes of their cologne. The 5¢ and 10¢ sizes were advertised on smaller cards (4.0" high by 2.5" wide). These trade cards are unusual because both sides are printed in color. As the new century progressed inflation hit and the original 10 cent cologne became the size of the original 5 cent cologne and a new 15 cent size was introduced."
www.cliffhoyt.com: "The cologne which was to make the name Hoyt famous was first developed for sale in his apothecary shop. The name "German" was originally applied to the cologne in 1870. This name was chosen just to give a definite title to the cologne. There was no intention (unless implied by the innocent buyer) that the cologne came from Germany or bore any resemblance to German cologne. The cologne initially was only sold in $1.00 bottles, with sample vials filled with cologne freely distributed to create an increased demand. By 1877, the production of the German Cologne became so all consuming that Hoyt sold the apothecary shop to two current employees, Crowell and Harrison, so that Hoyt & Co. could devote their full time and energy to producing and selling cologne."
At www.wolfcreekarcheology.com :
"Hoyt’s German Cologne was introduced in 1870 by E.W. Hoyt. Hoyt
began working at E.A. Staniel’s apothecary shop in Lowell Mass. at age
13 (1851). When Staniels died in 1861, Hoyt took over the business.
He developed the cologne at the shop but by 1877 the cologne
business had grown so large that he sold the old shop to concentrate
on the cologne business. His partner F.B. Shedd was the marketing
wizard behind the product. Hoyt died in 1887, the same year Shedd
brought out Hoyt’s “Rubifoam” tooth wash (Hoyt 2005)."