Photo via Wikimedia Commons (SM9 shown; SM7 shares the boxy third-generation body)
One example. Colors, sub-models, and production years vary; the machine you find may differ.
"the carriage-shift SM3 mechanism with later refinements; sweet spot between SM3 and SM9"
— collector consensus
External, in their original form. The people who know these machines best — click through to read and watch.