Ct-1 bond in sealed envelope

We are a manufacturing unit exporting goods through merchant exporters against CT-1 bond and ARE-1 given by merchant exporter.

Till now the merchant exporters were sending two copies of CT-1 bond directly to us through courier in a normal envelope.

Now from last one month our local excise office is insisting that the CT-1 bond should we given by merchant exporter in sealed envelope with govt. seal from their excise department.

I am aware of such process for ARE-1 after disptach of goods i.e it is to be given in sealed envelope with govt. seal.

But is there is any written rule for CT-1 bond in sealed envelope or is the our excise office unnecessarily asking for it.

Can someone please clarify on this matter.

Thanks in advance,

Regards,

Rahul