%w( Archive201001 Archive201002 Archive201003 ).each do |tablename|
eval <<-END_EVAL
class #{tablename} < ActiveRecord::Base
end
END_EVAL
end

Now

Archive201001.count
Archive201002.count
Archive201003.count

should all work. Looks a bit silly.

Other way,

%w( Archive201001 Archive201002 Archive201003 ).each do |tablename|
Test.set_tablename(tablename)
res = Test.find( :all, :conditions => "name like 'test%'" );
puts "Total results from #{tablename}: #{res.size.to_s}"
end

(Haven't run the code / might have some syntax error still.

Stephan