The MS-2000 (M)™ distress marker light has come a long way since you purchased ACR's original Firefly® back in the 1960s. 

Attached infrared (IR) filter for Night Vision Goggle (NVG) viewing. Directional, shielded blue filter. Identifies strobe from ground fire. Raised polarity indicators allow correct battery replacement even when visibility is low. Omnidirectional white strobe emits brilliant 250,000 peak lumens. Compact, lightweight and waterproof to 200 feet. Large sliding switch for easy operation under any conditions. Battery door attached to case to prevent loss. Shield extends/retracts for omni- or uni-directional visibility. IR filter blocks all visiblelight (lets through only IR light). Raised polarity indicators allow correct battery replacement in low or no visibility conditions. New braided steel retainer keeps battery door from being lost. Operates on 2 standard alkaline AA batteries - disposal causes no environmental impact For extreme cold environments or long term storage, use 2 common lithium batteries. Blue filter distinguishes strobe from ground fire when in place.

Size: 4.5 x 2.2 x 1.1 in (11.4 x 5.6 x 3.3 cm)
Weight: 4.0 oz (115 g) without batteries
Light Output: 250,000 peak lumens per flash
Flash Rate: 50 ± 10 per minute
Light Dispersion: White-omnidirectional, IR-omnidirectional, Blue-unidirectional
Operating Life: 8 hours minimum-strobe; 2 hours minimum-incandescent
Visibility: Military tested at a distance of 6 miles (9.6km) on a clear dark night
Waterproof: To a depth of 50ft (15.3m); 200ft (61m) diver version available
Batteries: 2 AA alkaline or lithium batteries (not included)
Case Color: Black with olive drab flashguard
Construction: Case, lens and flashguard-high impact polycarbonate; IR filter-butyrate
Activation: Spark proof magnetic reed switch.