Scald and peel the tomatoes, cut into pieces and remove the seeds. Put them to cook in a large kettle.. Bring to a rolling boil, lower heat and continue to cook. As they cook, the solids will settle and almost clear water will rise to the top. Remove as much of this as you can, so the sauce will be thick and not runny. When the tomatoes are fairly thick, add the onions, red peppers, celery and garlic. Blend the mustard with a little vinegar and add the mustard paste, vinegar, brown sugar, salt, pepper and the allspice which has been tied in cheesecloth. Cook gently 1 1/2 hours. Remove the spice bag after the first half hour. Taste and add seasoning if needed. Pack into hot sterilized jars and seal at once.