A Late Roman Lead seal in the image of a late Roman Emperor, as attested by crown visible with the center jewel.  The image is very late Roman in style, with the head/face on image, that begins to be common on some later roman coins beginning under Arcadius (383-408 AD).  Also the features and style of the image are very reminiscent of later roman mosaics and engravings.

There are letters visible around the head area, which are somewhat difficult to make out:

Option 1: [THEO]DOSIV[S] 402-450- AD

Option 2: [C] ONSTA [NTIVS]   420 AD

The image does share a striking resemblance to Theodosius I (or second possibly)

The lead seal was used to secure Imperial shipments, which may have included gifts or bribes to other foreign powers, or for supplies to the troops. Finding one with part of an insclription on it is quite rare and unusual.  The hole on the reverse is still visible showing where the wire or binding was put through the lead.

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