H.Nathan and co where part of a group of companies owned by the Australian company called Hoffnung and Co their buisness was primarily based around the importing and sale of goods through catalogue they where importers among other things of sewing machines and parts, and Swiss and American watches and all forms of gold and silver jewellery and display cases for retail jewellers.
They where a very large concern and supplied goods in Australia, New Zealand and Tasmania , Fiji and Honolulu and had huge warehouses across Australia.
H.Nathan and Co was the company's London based subsiduary they where responsible for purchasing goods in Europe and America and arranging the importation to Australia they would have been responsible for the purchasing and importation of your watch, they would not have been the manufacturer of your watch as such but would have sourced them from manufacturers in Switzerland and stamped them with the company name, the earliest reference to Hoffnung and co I can Find is 1872.
I think they would have been the Australian equivalent of Sear's Roebuck catalogue in America.
Just to add to the above since writing this I have learned the company was formed in 1851 and went out of buisness in 1980.
Yes that is correct. Looking at this photo you can see which strike side would operate the hammers. They would also need the springs to be the right force to run together, to compensate this the two hammers are lighter than the single one.
Some useful sites in case you havn,t visited so far.
Most recommended source is cousinesuk.
Yes manufacturers recommend routine M/S replacement. Manual winding gives you an idea how well the spring feels, to say the least eliminates selfwinding mech form diagnostic guestimation.