Along with the introduction of a solid battle story, it was the OJR line that also gave rise to designations. Using a series of letters and numbers before the Zoids name denoted it's allegiance (Republic or Empire) as well as it's power source be it battery or wind up.
The first letter:
Designated the Zoid's loyalty and used the letters "R" to represent the Helic Republic, "D" to represent the Guylos or "Dark" Empire, and the letter "E" which referred to the Zenebas Empire. (Note: Far later in the story line the Zenebas Empire would eventually be merged and become known as the Guylos or Neo Zenebas Empire.)
The second letters:
Designated the Zoids power source/series, and decoded as follows:
"MZ" or "Motorized Zoid"
"PZ" or "Powered Zoid"
"HI" or "Hi Powered"
"BOZ" or "Battery Operated Zoid"
"TFZ" or "Trans Fighter Zoid"
Several discrepancies exist with these abbreviations suggesting a drastic change somewhere along the line. It's my belief that the line was doing very well (compared to the American and European releases) and was expanded very quickly during mid release. Take, for instance, the Deathsaurer which should have been designated as an Empire Battery Operated Zoid or "EBOZ" but was instead designated as an Empire Powered Zoid or "EPZ". This error could also have steamed from the switch to actual battery powered motors instead of simple wind ups. There are far too many examples of second letter set errors for them to be simple marketing or print mistakes, but without hard release dates it's nearly impossible to speculate the exact source of the second letter error mystery.
The number (s):
The last part of the Zoids designation was a number. Staring with 001 and continuing up. Including the three exclusive Trans Fighters, the Helic Republic consisted of 51 Zoids, while the Empire totaled 39. Although not as heavy in errors as the second letter designations, flaws do exist including some non sequential and repeats of which Gustav and Shield Liger are probably the most spotted both having the designation of RPZ-02.
The last letter.
Very rarely a solitary letter follows the release number. This number indicates that the Zoid is a second generation or MK II of the original piece. Probably the most famed unit using this "last letter" would be the Iron Kong MK LTD with a designation of EPZ-002R.
The Original Japanese Release (which includes the Grade Up sub-line) would take the Zoids toy line far beyond it's time. The battery operated units are pinnacles of engineering and (in my opinion) rival many of the toys on the market today. Not screwing with something that was already perfect would give rise to most New Japanese Release Zoids.
RPZ-01 Salamander Salamander F2
This has been a Zoid.US production. No image may be used without permission. 2010 -WIKD