Interesting item! Personally, I would call it a spacer, or perhaps a rack spacer.

I think of lammers as round disks, usually a little smaller than standard size chips, sometimes with a beveled edge ... and with a number on it. Used by a pit boss or manager, or chip runner when he/she picks up cash on a game in order to replenish it with chips. Say a table has $620 in cash; the pit boss puts a 500 + 100 + 20 lammers on the table; takes the cash to the cage, gets $620 in chips and returns them to the table, then picks up his lammers.