1) Certain specialist 
A broker on the floor of an exchange or in the over-the-counter market (OTC) who trades bonds.
A broker on the floor of an exchange who trades bonds.
A bond broker acts as your agent, calling around to different bond dealers to find the best prices for the bonds you want. Brokers may charge a fee for their services or simply make money by increasing the markup, or the spread between the purchase and sale price of a bond.