The 100 was a lawn tractor and it replaced the 70 lawn tractor. The 100 made some improvements on the 70, most notably the 8 hp Briggs. Also the 100 came out with engine side panels as this was the next great thing in 1975, "quiet" was the word for that day and all the industry was moving to making quieter lawn equipment.
The isn't that rare, a lot of them were made and that and it being a lawn tractor, isn't as collectible as the older JD
equipment. The 100 was the last JD
model to have the round fenders though. And it was more solid and durable than the line that replaced it. In 1979 Deere replaced the 100 with two lawn tractors, the 8 hp 108 and the 11 hp 111 models.
Btw, the hood on the 100, like all JD
hoods of that day were fiberglass, not cast iron nor stamped steel. Here is the write up on the 100 model from WFM.The John Deere 100 Series Lawn Tractors The Model 100
The model 100 was introduced for the 1975 model year and replaced the model 70 as the only Lawn Tractor offered in the Deere lineup. As with most lawn tractors, the model 100 was primarily designed for mowing, snow removal & light grading work. Unlike the larger Garden Tractors, the model 100 was not designed or intended for use with ground engaging equipment (i.e., tillers, cultivators, etc.). The model 100 retained most of the basic design features that had been successfully utilized on the previous 60 and 70 lawn tractor models. The chassis, drive train, power take-off (PTO), steering and manual lift linkage remained fundamentally unchanged. Prominent features of the model 100 included: 8-HP Briggs & Stratton model 190707 engine 3-speed Peerless 1200 series transaxle Cup/Cone Power Take-Off (PTO) clutch Manual lift linkage One piece fiberglass combination hood/grill Engine side panels (for aesthetics & noise reduction) Wide footrests (similar to pre-1968 110/112 design) Round fender rear deck (like 60/70 models) Power transfer to the transaxle was accomplished via a two-belt system. The primary belt transferred power from the crankshaft to a mid-mounted, two-pulley counter sheave. The secondary belt transferred power from the counter sheave to the transaxle. Tension on the secondary belt could be controlled via the clutch pedal (located on lower left side of pedestal), which was coupled to the secondary belt idler pulley. It should be noted that the counter sheave pulley geometry was fixed and was not a "variator" sheave design (as used in the 110/112 & original 200 series). Braking was accomplished through application of the brake pedal (located on lower right side of pedestal), which caused a brake band to tighten around the brake drum attached to the transaxle brake shaft. A lever located on the upper right side of the pedestal controlled the single pulley manual PTO clutch. Both the manual lift linkage and the tractor accessory attachment points remained unchanged from the previous designs, which permitted continued use of the model 60 and 70 attachments. Deere attachments & accessories marketed for use with the model 100 included: 34 Rotary Mower 32 and 32A Snow Throwers 40 Front Blade (42-inch straight cut) 31 and 38 Lawn Sweepers (pull behind) 50 and 80 Dumpcarts 5B Sprayer Rear wheel weights & tire chains Chrome front & rear wheel covers Hour meter Kit The basic design of the model 100 remained unchanged throughout its four-year production run although some minor changes did occur. No headlight option was ever offered. The estimated weight was 470 lbs when equipped with the model 34 rotary mower and 390 lbs w/o the mower. The serial number ranges for the model 100 production years are as follows: Year Serial Number Engine 1975 30001-55000 Briggs & Stratton 190707 (8hp) 1976 55001-70000 Briggs & Stratton 190707 (8hp) 1977 70001-80000 Briggs & Stratton 190707 (8hp) 1978 80001-95000 Briggs & Stratton 190707 (8hp)