Investments may be made in bonds, notes and stock issued or guaranteed by any foreign government with which the United States is at the time of sale or offer of sale of the bonds, notes or stock maintaining diplomatic relations and which foreign government has not, for at least thirty (30) years prior to the making of the investment, defaulted for more than thirty (30) days in the payment of any part either of principal or interest of any bond, note, stock or other evidence of indebtedness issued by it; provided, that if the foreign government has not been in existence for as much as thirty (30) years, but has been in existence for not less than ten (10) years, then the investment may be made in securities issued or guaranteed by it, if it has not defaulted in the payment of any part either of principal or interest of any bond, note, stock or other evidence of indebtedness issued by it since it has been in existence.