I have two Compacs and an Interapid. Two were purchased as NOS (new Old Stock) and one as used but in great condition, all where about 1/2 the price of new ones. They all work great. A few things to also consider is the the range and reversibility of the indicators. If I recall some of the older ones had a reversing lever, many are limited to +/- one revolution which can be a challenge when dealing with the higher resolution models. The extended range is a great help when you are trying to get your work dialed in and the TIR is fairly wide to start with. With the Compac and Alina, you use to be able to pick them up on Fleabay for a lot less, but not so these days since they are now associated with Interpid. The newer Interapid, Compac and Brown & Sharpe I believe are the same, and just cross branded. You sometimes get lucky with buying used ones, but most of the time they have been abused which is often seen as the pointer neutral position has been knocked out of alignment. Alternatively when I have purchased a Chinese knockoff measuring tool, it has either broken and/or it does not work smoothly. After a few earlier experiences, I avoid any tooling from China when possible. I just had this problem with two Shar'sR8 collets that I use for my metric center finders and had some repeat measurement issues, both where out almost 0.001". I have a set of English Lyndex R8 collets, and the concentricity is 0.0002". The challenge was then to try to get two close tolerance replacement metric collets. Ended up purchasing two UK Crawford collets. Unfortunately they are no longer produced, so when they are gone I guess that just leaves Lyndex. I have been looking for a 0.0001" test indicator model for some time, the newer Interpid's have gotten very pricey, even the NOS and lost a few bids. The Compac 214 and 215 models at 20% off through Long Island Indicator are pretty sweet and a lot less than the Interapid equivalent models. So I recently picked up a Compac 215GA from them that I needed to setup some of my centering indicators. Compac test indicator with a long contact point that I use on the lathe to center stock in the spider. Love this one because of the wide range, it was perfect for this application. Interpid test indicator and Starrett dial indicator setup for my QCTP.