A 76-year-old male presents with intermittent fever and low back pain for 5 months. Laboratory tests show Hb 76g/L, normal WBC and PLT, urinary protein (+++), Bence Jones protein (+), no M-spike on serum protein electrophoresis (SPEP), IgG 4g/L, IgA 0.9g/L, IgM 0.6g/L, undetectable IgD and IgE, bone marrow plasma cells 56%, and L1-L3 vertebral compression fractures on X-ray. A diagnosis of multiple myeloma is made. What is its type?