Hi rafterfind.
The Energex began as an upright vacuum cleaner that dates back to 1918, and was sold through the Sears and Roebuck catalog. In later years, tank and hand vacuums as introduced as well, and sold under the names Commander, Franklin, and Kenmore.
In the early 1990's John Lucia, co-founder of the Vacuum Cleaner Collectors Club did extensive research on the vacuum cleaners sold through the Sears and Roebuck catalog. Once his research was completed, he put together a two part report, mostly copies of the pages in the catalogs from 1909 - 1942, and another from 1943 to the early 1950's. He introduced that to us at the anual club meeting in 1993. I have the first part here on my desk, and the other part in my box of archives that I'll get tomorrow.
The one you have looks like an early Commander, but under the Energex lable. I'll know more when I locate the second part of the report, and can back it up with the actual ad. My off the cuff guess is that it's late 1920's. If there are any patent numbers with dates, then look for the last year, and it will give you a time frame. But no doubt about it, it's old.
Do you have the hose, wands and attachments to go with it? if so, then display them with the machine.
More info when I read John's report.
Alex Taber.