As Andy says
All the ECUs are original Nissan "OEM" . Blitz,Mines,ect do not and did not ever manufacture these units. All as they do is re-programme them by installing another (E)PROM into the existing unit. Most "99.9%" of these maps are not meant to be used with low octane UK fuel. Jap fuel has a much more refined higher RON rating and the US, much lower.
If you remove this (E)PROM from the unit then it becomes a bare STOCK OEM Nissan ECU. if you then place a new chip with whichever program....guess what......you got it:p
So a Blitz, Mines, Tommi, Barbie, Ken ECU are STOCK Nissan ecu's with incorrectly mapped (E)PROMs.
There not worth any more than other ECUs
PS...Before you boys tell me that you have the above ECU and your Z does 200mph in first gear, mabee so but serious damage can occur to your engine if your fuelling is not correct especially when you turn up the boost.