For those who may be interested . . . was able to find alldata (courtesy of deutschland mechanix - great guy/guys) statement that the collar cannot be removed once placed in position. Had to cut into collar so I could pry off & access tumbler (which had worn down to point that die cast at top of tumbler cracked apart).

To remove tumbler you need to access horizontal metal piece in tumbler w/ wire to pull in (retract) so tumbler will fall away. Cannot really get to that part except from topside & must remove the collar to do that move.

FYI for anybody having a problem w/ their key getting stuck between positions 1 & 2.