ONE APPROACH TO THE PROBLEM OF ESTABLISHING THE APPROXIMATE DATE ON WHICH A TYPED DOCUMENT WAS PREPARED HAS BEEN TO STUDY THE DEVELOPMENT OF TYPEWRITER DEFECTS OF A GIVEN MACHINE OVER CALENDAR TIME USING A DATED SERIES OF DOCUMENTS PREPARED ON THAT MACHINE. HOWEVER, WITH SINGLE-ELEMENT TYPEWRITERS SUCH DEFECTS ARE USUALLY LIMITED TO ALIGNMENT CHANGES, THE STUDY OF WHICH MAY BE VERY COMPLEX AND TIME-CONSUMING. A MORE RAPID DETERMINATION MAY BE MADE BY STUDYING RIBBON INK DYE TONERS OF THE TYPED IMPRESSIONS ON THE DOCUMENT IN QUESTION AND COMPARING THESE WITH DYES EXTRACTED FROM TYPING DONE ON THE SAME MACHINE ON A SERIES OF KNOWN DATES. THE MOST EFFICIENT ELUENT HAS BEEN FOUND TO BE 100 PERCENT PYRIDINE ADMINISTERED WITH DISPOSABLE MICROPIPETTES OF ONE TO TWO LAMBDA SIZE. THE DYES ARE ELUTED DIRECTLY ONTO THE THIN LAYER PLATE STATIONARY PHASE BY PLACING THE 1-MM SAMPLE DISC DIRECTLY ONTO THE SPOTTING AREA OF THE TLC PLATE AND RUNNING THE ELUTION SOLVENT THROUGH THE SAMPLE DISC. USUALLY 1 TO 12 ONE-MM DISCS PUNCHED FROM THE TYPING TO BE ANALYZED ARE USED, DEPENDING ON THE DEGREE OF ANALYTICAL DETAIL REQUIRED. GLASS 20- BY 20-CM TLC PLATES WITH A 0.25-MM 1 LAYER OF SILICA GEL '60' WITHOUT FLUORESCENT INDICATOR ARE RECOMMENDED. THE SAME SOLID PHASE COATED ON ALUMINUM OR CLEAR ACETATE PLATES HAVE ALSO BEEN USED WITH EXCELLENT RESULTS. THE MOST SUCCESSFUL LIQUID PHASE CONSISTS OF 70 PARTS BY VOLUME OF ETHYL ACETATE, 35 PARTS ETHANOL, AND 30 PARTS DISTILLED WATER. FOR GENERAL PURPOSES ROOM TEMPERATURES ARE SATISFACTORY. RUNNING TECHNIQUES INVOLVE 24- TO 74-HOURS DESSICATION BY STANDARD METHOD. CARE SHOULD BE TAKEN TO SATURATE THE ATMOSPHERE OF THE RUNNING TANK BEFORE EACH RUN. AIR DRYING AND DESSICATION BETWEEN RUNS IS STANDARD. AS MANY AS SIX SEQUENTIAL RUNS HAE BEEN USED IN SOME ANALYSES. AN AVERAGE RUNNING TIME FOR A FIRST IMMERSION HAS BEEN 10 MINUTES, FOLLOWED BY 45 MINUTES AIR DRYING, AND THEN 30 MINUTES TO AN HOUR IN A DESSICATOR BEFORE EACH SUCCEEDING RUN. CARE MUST BE TAKEN THAT RESIDUAL PYRIDINE DOES NOT BECOME PART OF THE RUNNING SYSTEM. COMPLETED SEPARATIONS CAN BE PRESERVED FOR YEARS IF MAINTAINED IN A DESSICATOR AT ROOM TEMPERATURE. THIS METHOD DOES NOT YIELD SUFFICIENT INDIVIDUATING ANALYTICAL DETAIL TO BE USED FOR IDENTIFYING A QUESTIONED TYPING WITH A KNOWN RIBBON. EXPERIENCE WITH CARBON COPIES HAS BEEN CONSISTENT WITH THAT FOR RIBBON COPIES. THE METHOD WORKS EQUALLY WELL WITH TEXTILE OR PLASTIC FILM CARBON RIBBONS. (JAP)