Armrest-to-armrest:
W210 53-1/2 inches
W124 52-1/2
W123 52

Based on the three cars in my signature box. These are worst-case measurements. If you could work around the armrests you would gain a couple of inches.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970