More messing with extension tubes

A short break in the rain in the morning coincided with cooking/eating breakfast and preparing the evening meal to leave in the slow cooker. By the time this was over it was back to rain so I messed about again with extension tubes on the same legacy lens as yesterday, putting on all the tubes I have, making 68mm in all.
Now very difficult to focus by moving the tripod back and forth as I did yesterday, so I dug out an old focussing rack.
To experiment I used the same 5p piece as yesterday but for those who don't know this smallest of current British coins I've put a grain of pearl barley on it. That's not in focus as, not surprisingly, depth of field is very shallow even at f/16. Even on the tripod, at this magnification I had to use the self timer to get rid of camera shake.
Now I just have to find something more interesting to blip for Tiny Tuesday, but not this week as my challenge for this will be thinking up something for the second week of  Dickens. Thanks so much for the comments, stars and hearts on my first week's effort.
50mm f/1.7 Zeiss Planar at f/16 with 68mm extension on FujiX Pro1.