A surety company authorized to do business under the laws of the State may be accepted as surety on the bond, whenever, in the opinion of the officer letting the contract, the rights of all parties in interest will be fully protected. If the surety or sureties on the bond, whether individual or corporate, shall be other than a surety company authorized to do business under the laws of the State, there shall be not more than four sureties who shall severally justify in such amounts as, taken together, will aggregate the full amount of the bond; provided that in the case of the other sureties the officer letting the contract shall require that the surety shall also severally deposit with the officer certified checks, certificates of deposit, or share certificates (unconditionally assigned or on demand on or after such period as the officer may stipulate) or bonds, stocks, or other negotiable securities, or execute and deliver to the officer a deed of trust of real property, all of such character as shall be satisfactory to the officer, each surety to furnish the security to the full cash value of one hundred per cent of the amount for which the surety shall so have justified; provided further that the contracting officer, in the officer’s discretion, may waive the necessity of furnishing the security, to any extent that the officer may deem warranted, in cases where, upon an actual examination, the officer is satisfied as to the financial responsibility of the proposed surety or sureties; provided that if there is but one personal surety the surety shall so justify for the full amount of the bond.