Now I think about it, Bridges ect also do not have input protection. You do not use 4 wire technic to polute measurements with protection devices ( sparcgaps, diodes and zeners have capacitance l inductance and leakage current)
But there is no warning on the cover or in the manual about overload ( or I missed it) and i looked for that.
I bought mine as a private person from IET direct. But I know someone ( from mail, helped me a lot with advise when restoring my GR1608) who used to work there for many many years. That helped probably. I do not know if they sell to private persons normaly.
I have seen the mastech video but there are many things different. Like the mastech des not work on 9 V, the IET does, the IET has autopower of, also for the backlite, the calbutton is on the front, where it belongs, the accuracy is given for each range separate including things like tempco but best is 0.3 % and mastech 0.5 % but I could not find more. And there are more small differenences. Like the guard output, banana busses, case. But indeed a lot of similarities in functions (like always when people clone something and want you to think it is the same) and the pcb is green and uses two chips. But I do not care, IET has a reputation to hold to, they will not gambe with that. They make c meters that cost over 20k Dollar, this is the only affortable instrument they make so it would be stupid to screw that up. So that is more inportsnt to me. Every time I made an other choise i have regretted it in the end. I had a rigol scope I hated, i had a Voltcraft LCR meter ( 180 euro) that I did not like, had a 250 euro Voltcraft scope meter that died making a mistake that did no harm to my Fluke ( because after the VC blew up I took my oldest Fluke and that only said overload. After the Rigol I desides not to buy B brands any more but save longer or buy a good used one from a A brand. So now I have bought new over some years: a very good 350 MHz Hameg DSO ( i love it), an Agilent 50K count hand multimeter that is still going strong after a lot of use and abuse and a Keithley 2000 i like and use a lot. The rest is second hand stuff, often restorred by myself and most bought for peanuts or got it for free. But all top instruments. Like Jim Williams writes in the first chapter of his book, there is nothing more educational as repairing ( and a picture with a scope under repair, a pizza and some drinks and the text with it, live can not become better then this.) and he wrote, i'm probably he only one on a flee market willing to pay more for a broken instrument as for a working one ;-)
The chipset is not visible on the teardown from dave so the guess is only it uses the same chipset. But it is also possible the cirrus is a copy of the IET or the IET is a custom version or better speced one. I think the potting is not to hide the readings , there are more easy ways to do that, but i would expect the potting has to do with more precision ( like potted or sealed resistors and caps to keep moisture ans leakage through dirt have less influence) I have seen boards in calibrators there were totaly coverd with a sort of potting layer. I had to replace a part on duch a board, i ad to use a drenel firs to remove his very thin film before I could desolder ( also have seen boards Printing : look out, do not touch, ultrasonic cleaned)
Hmmm, another piece of consumer electronic shit died on me, now I have to look to my router. It is constantly stops the wifi