A Russian defence firm says an old Buk missile it used to manufacture brought down Malaysia Airlines flight MH17 over eastern Ukraine on 17 July 2014.
The Almaz-Antey firm said the Buk M1 guided missile was fired from an area south of Zaroshchenske.
The statement is in line with previous Russian claims that Ukrainian forces, not the rebels, fired the missile.
The destruction of MH17 - a Boeing 777 - killed all 298 people on board. Ukraine blamed the pro-Russian rebels.
There is controversy about who controlled the Zaroshchenske area at the time. The Russian military said the town was under Ukrainian military control, whereas Ukrainian officials insisted it was already held by the rebels.
Almaz-Antey said it had analysed shrapnel damage and identified the missile as "9M38M1 of the Buk M1 system".
The firm's CEO, Yan Novikov, said the missile was withdrawn from production in 1999 and "the concern and its companies could not have supplied these missiles to anyone in the 21st Century".
The wreckage fell in an area controlled by pro-Russian rebels. Ukraine and Western investigators suspect that rebels, armed by Russia, fired the missile.
Ukraine has denied Russian claims that Ukrainian forces were equipped with Buk-M1 missiles in that area.
International investigators say a Buk missile launcher was seen being driven through the rebel-held town of Snizhne only four hours before the plane was shot down.
Last year Russian officials had alleged that MH17 was shot down by an air-to-air missile fired from a Ukrainian SU-25 fighter jet, but that theory was widely discredited.
Then, last month, a leaked report by Russian military analysts, published by independent newspaper Novaya Gazeta, said a Buk-M1 missile had brought down the plane, asserting it had been fired from Zaroshchenske, some 24km (15 miles) west of Snizhne. That theory was put forward by the Russian military as early as 21 July 2014.
Almaz-Antey refused to comment on who controlled the launch site at the time, but insisted that the Buk could not have been fired from the Snizhne area.
Mr Novikov said the firm was willing to stage "a full-scale, real-life experiment attended by independent observers and experts" next to a similar Boeing 777 fuselage, to reproduce the MH17 impact.
On Sunday a forensic report by analysts in the Bellingcat research group said satellite photos presented as evidence by the Russian defence ministry had been falsified.
The images, published by the ministry on 21 July 2014, purported to show Buk missile launchers near Zaroshchenske on the day of the MH17 disaster.
Bellingcat says they were "digitally modified using Adobe Photoshop CS5 software" and the dates were altered.
Most of the MH17 victims were Dutch. The Dutch Safety Board will present its findings by October 2015.