What a watch “377” means
Watchmakers and retail packs often print a three-digit trade number (301, 364, 377, 395…). That number is a size label for a 1.55V silver-oxide button cell — not a lithium CR2032-class coin.
The same physical cell also carries an IEC code such as SR626SW. Brands print Renata 377, Energizer 377, Duracell D377, Varta V377, and SR626SW for one size family.
Use the empty cell or the movement documentation. If the OEM specifies silver oxide, do not substitute alkaline AG/LR twins for longevity-critical watches.
Common trade number → IEC map
301 → SR43 · 303 / 357 → SR44 · 309 / 393 → SR754SW · 315 / 314 → SR716SW · 317 → SR516SW · 319 → SR527SW · 321 → SR616SW · 329 → SR731SW.
335 → SR512SW · 337 → SR416SW · 339 → SR614SW · 341 → SR714SW · 344 / 350 → SR1136SW · 346 → SR712SW · 348 → SR421SW · 361 / 362 → SR721SW · 363 / 364 → SR621SW (drain class differs — see notes on the battery page).
365 / 366 → SR1116SW · 370 / 371 → SR920W · 372 / 373 → SR916SW · 376 / 377 → SR626SW · 379 → SR521SW · 380 / 394 → SR936SW · 381 / 391 → SR1120SW · 384 / 392 → SR41 · 386 → SR43 · 389 / 390 → SR1130 · 395 / 399 → SR927SW · 396 / 397 → SR726SW.
Open the matching battery page on this site (search the trade number or SR code). Mappings follow industry Renata/IEC cross-reference tables used by jewellers — always confirm the empty cell.
Silver vs alkaline
Shop AG / LR labels (AG4, AG13, LR626…) are often the alkaline twin of an SR size. They can fit and still be the wrong chemistry for a silver-specified movement.
CR / BR lithium coins are a different system entirely — a watch “377” is not a CR2032.
Quick takeaway
Read the three-digit code or SR code on the empty cell → open that battery page → match silver oxide when the watch requires it. Use brand watch hubs (Casio, Seiko, Citizen, Orient) when you know the model.