Hi,
I'm no gun expert but I did a net search using altavista...it looks like your gun was made by "Boito" in Brazil.
The address to their homepage is:
www.eramantino.com.br the english version has broken picture links...brush up on your spanish
Also, the search turned up some kind of gunlist: it's at
http://www.leds.state.or.us/resource.../gun_codes.pdf
If you look under "era" it says brazil and boito.
And, the gunnersden.com seems to have some kind of era schematics for sale...
Also,
www.gun-parts.com/stocks/ makes a reference to the era shotguns as being distributed by k-mart.
Hope this helps some and doesn't just lead you in circles more.
-Beetle