Old favourite

Most utilised lens at its most usual settings. f 6.3 focused between 10 ft. and infinity. Looking slightly worn but still going strong after owning it for 50 years.
Could also sell it for more than it cost.
Don't Imagine many current lenses would last that long.
Leica+24mm+f2.8+elmarit-R.
For mono Monday - had to leave the red dot.