In addition to the ET-1010/1070/1080/1090, Wheelock produced the ET-1011/1071/1081/1091 according to this CSFM listing. The ET-1011 and ET-1081 are also UL listed, and the ET-1081 is mentioned in a manual for the SM. However, there is very little documentation of these devices online.
I previously suspected that these were the slow whoop signals mentioned in the late 1980s catalog, since they are shown together with the speakers. However, I recently discovered this article, which lists models ET-1081-LS-VFR-HON, ET-1081-LSM-VFR-HON, and ET-1081-IS-VFR-HON as being replaced by ET80 models. I assume the -HON suffix refers to the fact that these are being rebranded by Honeywell, but other rebrands such as the ET-1080-LSM-24-VFR-RAD use the standard ET-1080 model number. Unfortunately, I could not find any information on Honeywell rebrands on older versions of Honeywell’s website.
I also saw that some pages on older versions of Wheelock’s website, such as this archived page and this archived page, mention the option for ET speakers to handle 100 volt audio. However, neither this feature nor the ET-1081 is mentioned on any datasheet I found on the Wayback Machine.