When I use dial calipers, I maintain the same thumb pressure, clean the
jaws, and zero often. I try to rock them into perpendicularity, and
measure with the same spot on the jaws each time. I check my accuracy
with pin gauges. I interpolate between the .001" hatch marks with my
eyes. My eyes can easily resolve .0002", but .0001" is harder.

0) My 8 year old Midway $20 Chinese 6" calipers can be trusted to .0002"
1) My new Enco $14 Chinese 6" calipers can be trusted to .001"
2) My new SPI $25 Chinese 6" calipers can be trusted to .0025"
3) My new Mitutoyo $72 Brazilian 6" calipers can be trusted to .0002"

The thing of interest was the $25 SPI looks like it is the same as the
$14, with nearly the same serial number sequence on the back. But the
SPI costs more and are not as good. The "SPI" name has been whore'd out
to Chinese junk.