A friend of mine whom I had trained in King Airs was recalled to United Air Lines and had a long career with them. He was scheduled for a layover in Phoenix years ago and asked if I wanted to come out to the gate with him before his morning departure to see this very aiplane, SN 1 he was left-seating that day. I did. What an old classic.
He pointed out that the DME was just that...it only read distance to the frequency it was set to, no GS or TTG. He went on to tell this cute story about his UAL ground instructor and himself. (Remember, this was WAY before GPS!)
When it came to discussing the avionics, the instructor commented that most of the class members were probably used to DMEs having GS readouts and the lack of one might be a worry. But no problem since you can do an easy six minute check: See how much the distance changed in six minutes. Since that is 1/10 of an hour, the answer was obvious. e.g., 56 nm in six minutes = 560 knots GS. Or, said the instructor, you could time for 36 seconds. Not quite as accurate but still OK. e.g., 4.8 nm in 36 seconds (1/100 of an hour) = 480 knots GS.
My friend said he raised his hand and said, "I can get a GS check in 3 seconds." "No, said the instructor, you cannot be accurate with such a short check!"
"Oh yeah?" said my buddy. "Here's how you do it: Uh, Chicago Center, what do you show for a GS for United XXX?"
Even the instructor got a chuckle.
