Netscape Communicator UserAgent Question

[beanboy89]

I have noticed some Netscape 4.x and 3.x UserAgents I have seen have seen have [tt]I[/tt] at the end, while others have a [tt]U[/tt] at the end, after the OS version.
Examples I have seen: [tt]Mozilla/4.51 [en] (Win98; I)[/tt] has an [tt]I[/tt] at the end, while [tt]Mozilla/4.51 [en] (Win98; U)[/tt] has a [tt]U[/tt] in the UserAgent.
What is the difference between the UserAgents with the [tt]I[/tt] and [tt]U[/tt] at the end, after the [tt]Win98;[/tt] section?

UserAgent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.7.2) Gecko/20040803

[Andrew T.]

Originally, Netscape browser releases for the domestic (U.S.) market contained encryption technology that, due to legal reasons of the time, was not present in international releases.

"I" indicates "International Security" (40- or 56-bit).

"U" indicates "United States Security" (128-bit).

UserAgent: Mozilla/5.0 (Windows; U; Win95; en-US; rv:1.7) Gecko/20040803 Firefox/0.9.3

[Antony]

Please see this Netscape encryption level (SillyDog701 Netscape Knowledge Base) for more info.

UserAgent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X; en) AppleWebKit/125.4 (KHTML, like Gecko) Safari/125.9