According to the Starrett web site, these gages "meet or exceed ISO accuracy requirements" but they do not specify or publish what those accuracies are.
The Starrett 708 and 709 series of test indicators have some idiosyncrasies that can make these repairs challenging. Unless you have experience and tools, we strongly urge you to leave this in the hands of professionals. Only the clear plastic cover (crystal and bezel assembly) and the contact points are easily replaced by the end-user (refer to notes at bottom of this page).
It is important to remember that these Starrett indicators are accurate when the contact point has an angle of about 10 to 15 degrees to the test surface. If, during calibration, you find that you are losing or gaining distance (even though the contact angle is correct) you will need to shorten or lengthen the contact point. The longer the point is, the less travel it will register. To do this, you will have to adjust the set screw which you will see on the opposite side of the pivot. Loosen the contact point first and then adjust the set screw. Now you can tighten the contact point again. Quite a bit of trial and error will get you the results you're after. If this is too much of a headache, next time don't buy Starrett.
Spare parts are not available from us because we are not Starrett distributors.
Repair hint: if you need to remove the guts from the body you will have to remove adjusting screw #8 first. Similarly, if you need to remove the dial head assembly #11 you will have to remove (or at least loosen significantly) adjusting screw #36 on the cover side. You can only find this screw by removing the cover. A very small jeweler's screw driver will be required.