The Australian Office of Financial Management has launched a 30 year Australian Commonwealth Government Bond, with a maturity of 21 March 2047. The AOFM said in preliminary email note that the initial issue would be "of a benchmark size". This is generally understood by fixed income investors to imply a minimum size of A$500 million. It will pay a coupon rate of three per cent.Initial price guidance, based on a three per cent coupon, was 100 to 107 basis points over the implied bid yield for the primary ten-year Treasury Bond futures contract. This implies an initial spread to US 30-year Treasuries of 70 to 80 basis points.The issue is expected to price today (12 October) for settlement on 19 October (T+5).ANZ, Citi, Commonwealth Bank of Australia, Deutsche Bank AG, UBS AG Australia Branch and Westpac Institutional Bank are joint-lead managers for the issue.The rates strategy team at ANZ Research - taking care not to be seen as making a formal recommendation on the new ACGBs - noted that this issue would continue a trend towards 'Methuselah' or long-dated sovereign bond issuance."Several sovereigns have come to the market with curve extending bonds: in mid-2015 Mexico issued a four per cent March 2115 bond," ANZ's rates strategists wrote in a note to clients. "Earlier this year Ireland issued a 100 year bond (2.35 per cent April 2116). Belgium issued a 2.3 per cent May 2116 bond and Spain issued 3.75 per cent June 2066 and 3.45 per cent July 2066 bonds."As recently as last week, Italy was able to issue a 2.8 per cent March 2067 bond, which was more than three times over-subscribed. The final size of €5 billion managed to attract an order book of €18.5 billion, mostly European instos, on the back of the relatively high yield offered by Italy.Standard Life Investments observed: "With so many bonds yielding less than zero (approximately US$12 trillion) - and even short-term Italian bonds trading at negative yields - investors are hard pressed to find the sort of yield this new 50-year bond offers. That's why it has been so popular."