Miles- from what I can see from your photos the back should come off from what you have done- yours isnât the 212 with hidden countersunk screws around the circumference of the boltcase. The perspective is a bit distorted and they do look a grainy/fuzzy, but it definitely looks like it should only have the large hexagon head bolts on the inside.
Look at where the boltcase- thatâs the box shaped part on the back of the door, meets the thin outer plate which has the dovetails or trapezium shaped blocks on. If you use a very sharp bladed screwdriver or tapered chisel to prise between the two halves towards the top it should open a gap. A few taps with a hammer and you should feel it bite in. Most of us in the trade have made ground HSS chisels to do this, but you can have a go with anything with a fine taper as long as itâs very tough- donât use a very thin screwdriver as itâll break- likewise donât use an ordinary wood chisel as theyâre only hardened carbon steel and if itâs seized really hard itâs likely to break off and leave the tip wedged in the gap.
You can also try a large block of hardwood- about 4 inches thick and a comfortable length to hold with fingers clear of the door- hold it on the back of one of the corners and give a firm thump with a dead blow hammer- âThumpâ against the hardwood block, not whack with a huge sledge against the metal! After a few goes it should loosen the gap and if itâs not freed it should still open enough of a gap to try the wedge method again. You can also try hitting on the top corner edge- different angles are more likely to free up a gap as long as you hit the block and not the safe!
Those Milners varied a lot with the fit of the boltcase and firepans on the doors- some would fall off once the bolts were removed, others were such a tight fit over the dovetail blocks theyâd become seized with age, corrosion and countless coats of paint.
Once the backs off, you should see the Milners block âpowderproofâ lock under a rectangular plate held with 6 very large headed countersunk screws- if the backs never been off youâll almost definitely need to use an impact driver or pin-punch to drive these around.
Good Luck đhappy):
