This is the front, obviously. I'll have a closeup on the stamps soon, I have to get back to work and dig out the original scan.

The address is obviously faked, the thing was mailed in Tucson (postmark gives it away) but made to look like it was coming from 133 Herman St, San Fran. We've seen this on Mar. 20, 1991. Its the San Francisco Mint.

Similar markings appear on Dec 4, 1990. This Greek? Hebrew? Huh? UPDATE: ashton kicks ass:

One more for you guys: the four letter word in Dec 4, 1991 and on
one of the mailing sent to Bryan is Hebrew.  M-F-T-CH, maphteach,
pronounced maf-tay-akh, means "key".
I also noticed that the first word of the second line of the quote 
from Ezra 3:13, he misspells "T-R-V-A-T" as "T-R-V-A-H" (Tav and 
He look awfully similar).  Indeed he kinda has a weird way of writing
Hebrew ... not that I am any expert, mind you.

So we assume this is some sort of hint pertaining to cypher(s), now, I guess...

It isn't Arabic, but here's a resource for later.