Got a shot at 1500' with a mini-prism not too long back.
Always beware when mixing gear from different sources. With the (very) old Kern rectangular prisms, used with a Geodimeter the constant was different depending upon which way up you had the prism ( on each axis - hence 4 constants!). We still have a couple we use occasionally on the back of the inflatable -no great financal hit if they ever fall off into the water. For that purpose a few cm. on the distance doesn't matter.