Java Edition:Portal (Item)
Portals as an item were obtainable in Beta 1.6 Test Build 3. They were deleted in 14w25a (1.8 snapshot). The portal item will disappear from all inventories, however, placed portals will still exist if a certain version range is followed,[test] but they will break if updated.
They can be placed in the End, unlike end portal items, which cannot be placed in the Nether nor the End.
Obtaining
Beta 1.6 Test Build 3 Debug Chests
In Beta 1.6 Test Build 3, any newly generated world would contain up to 11 debug chests with every item in the game. The portal item was obtainable in the chests 4th and 7th from the left in the 5th and 16th slots respectively, in stacks of 64.
It may be possible to obtain these items in 1.7, as theorized by JKM (a mastermind behind AFB).
Behavior
In Beta 1.6 Test Build 3 through [test] the item appears as a full block in the inventory until placed when the item model is then updated to look like the normal block form. When any block is placed next to the portal, the block will update and the portal will break.