Panther 1900-1967. Panther motorcycles were manufactured by Joah Phelon & Richard Moore originally called P&M. They patented the idea of using the engine as a stressed member of the frame in 1900 and were the first to offer a two speed gear with chain drive as standard equipment in 1904. Panther manufactured big 600cc bikes (646cc by 1964) that were among their most famous. Promoted as the "Perfected Motorcycle," they were known for innovative designs, but despite this, they were fairly simple and robust machines. Their low torque made them ideal for pulling sidecars along, but when sidecars lost popularity in the 1960s, so did Panthers with their outdated design and they succumbed to the tide of Japanese imports in 1967.

Click the photo to see a full size version, see reviews at bottom

1950 Model 100
600cc

1957 10/3
197cc

1958 Model 35 
250cc

1959 Model 35 
250cc

1959 Model 45
325cc

1960 M65 
350cc

    
 

Panther Model Review

Model 100 1946-63, 598cc, ohv single, 440lb, 60mpg, 75mph
A long stroke 600cc single that used its engine as a stressed frame member. Intended as a sidecar mount where it works well and it looks quite odd without one. Huge flywheel meant acceleration was slow but once going it would keep its speed up against almost any  obstacle.

Model 120 1959-65, 646cc. ohv single, 440lb, 55mpg, 80mph
Enlarged Model 100, but otherwise little difference. Notably more trouble than the Model 100.

Model 10/3 & 10/4 1956-1960, 197cc Villiers 8E & 9E
The Model 10/3 made from 1956 to 1960 used a 197cc Villiers 8E/3 unit construction two-stoke engine developing 7.5 bhp at 4000 rpm. 
The Model 10/3A and Model 10/4 used the Villiers 9E/3 and 9E/4 units developing 8.4 bhp. The /3 indicates a three speed model, the /4 a four speed. 

Model 35 ES 1958 to 1966, 250cc Villiers 2T
The Model 35 was manufactured from 1958 to 1966; the electric start (ES) variant only in 1965 and 1966.
Powered by a Villiers 2T, two-stroke twin 249cc engine with a compression ratio of 9.4:1 and a claimed power output of 15 bhp at 5500 rpm. 
Early Model 35s used Earles leading-link front forks as on the 1959 Model 45S above. From 1960 to 1964 they were fitted with the P&M telescopic forks fitted to the Model 65/75 four-stroke lightweights. For 1965 and 1966, they were apparently fitted with down-rated P&M Model 100 forks.
This model was produced when P&M were in deep trouble. Apparently the Electric Start model was only built because engines happened to be available at the right price. The exhaust pipes are Siamese to save the cost of one silencer. Apparently on these final batches the factory ran out of frame lugs and simply bashed the frames tubes flat and tacked them together! Specifications on these latter day bikes seem to have been highly variable with the factory fitting whatever they had to hand. 
Standard paint scheme was green; red finish was for Red Panthers sold through Pride and Clarke. The tank is a standard Speedwell unit; mudguards are polished alloy. 

Model 45 1959 to 1963/4, 324cc Villiers 3T
The Model 45 was manufactured from 1959 to 1963/4 powered by a Villiers 3T, two-stroke twin 324cc engine. 
P&M used the tuned Villiers 3T with a compression ratio of 8:1 and a claimed power output of 18 bhp at 5500 rpm. 
Apparently the 3T unit was developed for light car, not motorcycle, applications. 
Early Model 45s used Earles leading-link front forks. From 1960 they were fitted with the P&M telescopic forks fitted to the Model 65/75 four-stroke lightweights, apparently because of a reluctance to go round corners! "Devil Red" was the only colour scheme. This was one of the very last Panthers in production. Not many of these machines were produced and fewer have survived. 

Model 65/75 1947-63, 248cc/348cc, ohv singles, 340/350lb, 75/65mpg, 63/72mph
A pair of very traditional British singles. Distinctly not sporting they were equipped with about the best telescopic-forks to have been made in Britain; Dowty’s ‘Oleomatic’ (pump-up air-sprung) units. Rugged, simple and very nearly immortal.