The bonds must be signed in the corporate name of the college by the chairman of the board of trustees of the college, under the corporate seal of the college attested by the secretary of the board of trustees. Interest coupons attached to the bonds must be signed by the facsimile signatures of these officers. The bonds may be issued notwithstanding that any of the officials signing them or whose facsimile signatures appear on the coupons have ceased to hold office at the time of the issue or at the time of the delivery of the bonds to the purchaser.